WIND TURBINE BLOGPOST

Wind Turbine Blogpost

Background: 

There are a few primary concepts a person would have to understand in order to comprehend the way in which my wind turbine functions. A few of the most important ones are ... 

• Electromagnetic Induction: Beneath my wind turbine are loops of wire. Not far away from these coils of wire are the magnets. The bottle is made to spin and the magnets move in and out of the magnetic field, creating a change in the magnetic field. This induces a voltage which can create a current! The current can be used for multiple different things, but in our generator, the current is directed towards trying to light a lightbulb. 
• Torque: Torque is the reason that the wind-turbine rotated! To get a torque, you need a Force and Lever arm. Force and lever arm are inversely proportional meaning that if one goes up, the other goes down. Therefore, we tried to have quite a long lever arm so that we wouldn't need as much force to make the fan blades turn. We used the cut open flaps on the bottle as the lever arms and the force was the wind from the fan. When working together, we got the fan blades to spin! 
• Friction: Friction was something that we had to be aware of in our wind-turbine creation process. Friction is the resistance that one surface of an object encounters when moving on another. To have a well functioning wind turbine, you need to have as little friction as possible. Have a smooth and sleek surface (using sandpaper on wood or cardboard to soften it) can make all of the difference in the speed an object can reach. 

Materials & Methods: 

• An abundance of copper wire (70+ loops per coil)
• Strong magnets (5 or 6 pairs)
• 2 liter soda bottle
• String
• X-Acto knife (& band-aids)
• Cardboard box
• Tape 
• PATIENCE!!!! 
• Circular platform (for bottle to rest on) 

(A and D) This is a picture of the completed wind-turbine. You can clearly see the opened flaps meant to capture the wind.

(B) In this picture you can see the coils of wire beneath the device.

(A and C) In this image you can see a the magnets evenly spaced around the spinning platform. You can also see the opened flaps up close that catch the wind.

Results:

1. We created 0.02 volts and 0.02 amps of current

1. Sadly we were NOT able to generate enough voltage/current to light a lightbulb. I think that this is because our device was a little bit heavy and if it was lighter, it would have been able to move faster and generate more voltage/current.

Discussion: 

I learned a lot from doing this wind turbine project. I think that the most important lesson I learned was to keep the plan very simple. In the beginning, Mark had many ideas with big metal parts and robotics pieces and in all honesty, I felt lost. I wasn't sure if all of these big shiny metal pieces were going to fit together, but because I didn't really understand, I didn't speak up. It was not until the day before the project was due that we realized our design was not going to work. This is when I finally spoke up and introduced the idea of a cardboard box and a much simpler and basic design. This idea worked out WAY better and ran smoothly and we were able to put together an awesome wind-turbine faster than we had ever expected. We didn't generate a whole lot of voltage and this is because of the friction we had along with the magnets not being close enough to the coils of wire. What did work really well were the fan blades and the string suspending the bottle. What I would do differently would be to cut bigger fan blades and have the magnets rotating slightly close to the coils of wire. Overall, I really enjoyed making this wind turbine and it was all worth it to see it spinning in the end! 

My Top Ten

The Top Ten Place I See Physics in The Bahamas

1. When I go home for any one of the breaks, one of the first things I do is go to the beach! Before this class, I never pondered the physics behind the rising and falling of the tides. Although, after a long year in Ms. Lawrence's class, I think I can explain why I have to move my towel a little farther up the beach as the day goes on. I found out the earth experiences 2 high tides and 2 low tides every day! This means that there are 6 hours in between a high and low tide, and a full 12 hours from a low tide to get back to a low tide or a high tide to get back to a high tide. The alignment of the moon with the earth are what cause our tides. There are two types of tides, Spring and Neap. Spring tides occur when the moon, sun, and earth are all in a line. Neap tides occur when the moon is perpendicular to the sun. A tidal bulge occurs because of the moon's gravitational pull on the earth.

2. At home, we eat a lot of fruits and vegetables. A lot of the time we will pick a nice arrangement of fruits including avocados, mangoes, bananas and starfruit and put them in a little bowl on the middle of our coffee table in the living room. This reminds me of Newton's Third Law which states that, "For every reaction, there is an equal and opposite reaction." This means that every time you exert a force on an object, and equal and opposite force is put back on you (like punching someone). These two forces are called action and reaction pairs. In this case, the bowl of fruit and the earth are not actually an action/reaction pair! The force between the bowl of fruit and the earth may be equal and opposite, but because we must take into account the table, it cannot be called an action/reaction pair. Although, if the fruit was taken off of the table and placed on the floor, the earth would be pulling the fruit down with the same amount of force that the fruit is pulling the earth up with. 

3. After a long day at the beach, before driving the boat home, I always beg my dad to take us to Green Cay. Green Cay is a small uninhabited island with a huge cliff on the ocean side. If you climb up the rocks (very carefully) you can make it to the top of the the cliff and jump off into the water below. After physics class, I began to wonder how fast I was really moving as I dropped down towards the clear water below. I now know that from just knowing the height of the cliff and my own weight, I could easily calculate my velocity at each second of the fall and how much distance I covered at each second. (EVEN MORE INTERESTING) If I got a running start, I could find out my vertical velocity as well as my horizontal. All of this information can be found out with the formulas:

Vertical

V=gt

d=1/2gt^2

v=at

d=1/2at2

Horizontal

(at constant v)

v=d/t

d=vt

(Actual picture of Green Cay ft. My dad & I)

4. At home, especially during the summer, the power goes out ALL THE TIME. It can be one of the most annoying things ever, and I thought it was a very common thing before coming to the United States. Our power companies try to save money by decided when to just shut off the electricity for our homes.... (fun, right?) No! Luckily, I live in a small neighbourhood and a lot of our homes are connected to a generator. In simplest terms, a generator is a device that is made of coils of wires and magnets. Generators have mechanical energy and turn it into electrical energy. Much like the wind turbines we made in class, generators rely on electromagnetic induction to generate power. This is the magnets moving through the coils of wire. Below is a picture of what it looks like when the power goes out.......

5. In the 6th grade we had a huge project called "Exhibition". In this project, we were allowed to pick virtually anything and do an extensive project about it. One of my classmates chose electricity. He final debut was sadly unsuccessful because of the intense humidity at home! She attempted to rub a balloon to her hair and stick it to the wall. Sadly, it didn't work out as planned. BUT if we had been it a colder, and more dry climate, it would have! This is what would have happened....

--> The balloon would be charged by friction when rubbed against her head. When it is brought towards the wall, the wall would polarize. This means that all of the positive charges in the wall would be drawn towards the negative charges in the balloon.

--> The positive charges in the wall would move as close to the balloon as possible while all of the negative charges in the wall would move away from the balloon.

--> The distance between the opposite charges (attractive) would be smaller than the distance between the like charges (repulsive).

--> F=kq1q2/d^2 : (Coulomb's Law) Since there is a greater distance between the repulsive forces, the force between them will be less than the attractive forces.

--> Therefore, the balloon SHOULD HAVE stuck to the wall! 

6. Have you ever experienced a really really REALLY bad hurricane? Well I have! Actually, multiple a year! Due to the tropical atmosphere in The Bahamas, we get hurricanes all the time. As you know, in a hurricane there is a lot of thunder and lightening. For this reason, it is smart to keep our electronics inside of a metal box so that if our house were to get struck by lightning, our devices would be okay. Objects such as DVD players and computers are put inside of metal boxes to protect them from getting an electric shock and breaking. Charges buildup on the corners of objects making them more susceptible to shocks, so if this object were to (lets say get struck by lightening) the wires and everything inside of it would get fried and it would be useless. But, if this object were to be placed inside of a metal box, it would be saved. This is because when the charges attempt to build up on the corners, the metal displaces them and they all become neutral. This keeps the device from having a sort of charge and keeps it safe from breaking. 

7. It takes a lot of effort to load up the car for a beach day with bags and coolers and a paddle board. This is where a ramp could really come in handy! If I was trying to load a cooler (200N) into my car using a ramp, I can find out how much force I am actually putting into it, with the help of my simple machine. (We must remember that a simple machine does not decrease the amount of work done overall, it just breaks it up into smaller increments by using a longer distance so that it feels easier.) If the ramp was 10m high and 10m I would solve a problem like this...

Work-in = Work-out

F-in • d-in = F-out • d-out

F • (10) / 10 = 200 • 10 / 10

F = 200N

8. NO ONE pays attention to the traffic lights at home. Almost everyone is a terrible driver and I can't count how many silly car accidents I have seen over the years. If Bahamian drivers did listen to the traffic lights however, they might know how they actually work. I sure do! This is how.... 

A traffic light knows to change because of the process of Electromagnetic Induction. Beneath the concrete, at a traffic stop light, there is a HUGE loop of wires. When a car moves over the wires, a change in the magnetic field is caused. This, in turn, induces a voltage. The voltage then causes a current and this current sends a signal to the traffic light telling it to change. 

9. When i'm at home, I love to take pictures! I never knew what went on inside of the camera until this year in physics class! A camera has 2 oppositely charged plates inside of it. These two plates are NOT connected. You add charges to each plate, thus increasing the Force and energy of the electric field between the plates. When you briefly connect the plates (push the button on your camera to take a picture) energy rushes from one plate to the next and a light is produced (flash.) You cannot use flash continuously because you need to give the charges time to build up enough to create light. 

10. Fishing is a major industry in the Bahamas! My dad, my uncle, and almost every one of our family friends goes fishing on a regular basis. Sometimes, I go with them. One time (over christmas break) I realized that when I was reeling in a fish, I was using torque. Torque is what causes rotation. An object needs two things to have a torque, a force and a lever arm. In this situation, I was the force and the fishing rod was the lever arm. If I had a super long fishing rod, I wouldn't need to exert a lot of force. Oppositely, if I had big 'ol muscles, I wouldn't need to have a long fishing rod.

AND THATS 10 THE TOP 10 PLACES I SEE PHYSICS IN THE BAHAMAS!!!!!!!

UNIT 7 SUMMARY

UNIT 7 BLOGPOST SUMMARY

Magnetism

In this past unit we covered A LOT of important information. The subtopics were ... 

• Magnetism (magnetic poles & electromagnetism)
• Forces on charged particles in an electric field (motors)
• Electromagnetic induction and common applications
• Generators and Energy Production
• Transformers and Energy transfer from Power company to Home

Magnetism -->

Magnetism included magnetic poles, electromagnetism, domains, magnetic fields, cosmic rays and compasses. The source of all magnetism is moving charges. 

1. There are magnetic poles at each side of the earth. It is important to remember that the South and North are opposite from what we generally know them as when you draw your diagram. To show the magnetic field lines through the N and S poles, you must draw the magnetic field lines from S to N, out and around the earth and then back down. 
2. Domains show whether or not an object is magnetised. We use many arrows going in the same direction to show that it is strongly magnetised and just a couple of arrows, but all going different directions to show that it is unmagnetized. 
3. A compass is a device that shows the same direction of the magnetic field
4. Newton's 3rd Law tells us that both sides of a permanent magnet have the same force
5. If you had to show the magnetic field lines around a current carrying wire, if the I —> back to front (down) <— I front to back (up)

Forces on charged particles in an electric field (motors) -->

In this section, we focused on Cosmic rays and motors

1. Cosmic rays are charged particles moving through space which cause the phenomena known as the Northern Lights. At the two poles on the earth, the charges are moving parallel to the magnetic field and thus, feeling a force. Therefore, these rays can enter the atmosphere. (Perpendicular would be deflected) 

2. A motor consists of two parts, a current carrying wire and a magnet. A current carrying wire feels a force in a magnetic field. Motors have electrical energy and mechanical energy. In class we made our own motors, and below you can see a short video of mine working!

3. This is also the unit that we learned about the right hand rule where the thumb=force, index= current, middle=magnetic field

Electromagnetic induction and common applications -->

Electromagnetic induction and what it can be applied to was a section that we spent a lot of time on.

1. Electromagnetic induction is the process in which an object feels a force without actually being touched by something else. We learned more about this with traffic lights, metal detectors, and credit card machines. E.G. --> Traffic light... Beneath the concrete, at a traffic stop light, is a loop of wires. When a car moves over the wires, a change in the magnetic field is caused. This, in turn, induces a voltage. The voltage then causes a current and this current sends a signal to the traffic light telling it to change.
2. It is almost the exact same thing in a credit card machine. There is a loop of wires in the machine. When the credit card runs through, it causes a change in magnetic field. The change in magnetic field induces a voltage. The voltage causes a current that carries the message to the machine and signals the machine to tell it who's card it is.

Generators and Energy Production -->

Generators are made of coils of wire and magnets. Generators have mechanical energy and electrical energy. A generator relies on electromagnetic induction (do not get this confused with a motor, a motor relies on a current carrying wire and a force in the magnetic field).

Transformers and Energy transfer from Power company to Home -->

The final topic we focused on was transformers. Transformers are what are seen on the ends of our computer and phone chargers. Here are some facts about transformers...

• Boxes that contain two different loops of wires
• There are step-down and step-up transformers. Step down have more loops of wire on the primary coil and step-up transformers have more loops of wire on the secondary coil.
• Requires AC --> It requires AC because in order to induce a voltage, it needs to have a changing magnetic field. Alternating current is a constant change in current which changes the magnetic field

MOTOR BLOG-POST

Building A Motor

This week in Physics, we learned how to build a very basic motor! The only supplies that we were allowed to use were...

1. A battery
2. Rubber band
3. Copper wire
4. 2 paper clips
5. A magnet

I had an EXTREMELY difficult time creating my motor. I'm not sure if it was a poor connection between the ends of the paperclip and the magnet, or if it was because my copper wire was not scraped the right way, but I was one of the last (possibly the very last) person to get their motor to work in my class. Although, when the loop finally spun, it was very rewarding. I will explain my process.

1. I picked my battery (one that looked new) and got two paper clips
2. I unbent the paperclips and tried to come up with a smart way to form them so that the coil of wire could rest on them without falling off. It took me a couple different tries to get a good design. I finally decided on one that looped around the coil so that it would not fall off.
3. Next, I secured the paperclips with a rubber band (wrapped around twice)
4. Then I took the copper wire and wrapped it around two of my fingers a couple of times leaving about 2 inches on each end.
5. Then, I took the coil and scraped each side so that it could have a good connection
6. Finally, I placed the magnet on the battery directly below (and as close as possible) to the wire
7. And then....... after many tries........ the coil spun!!

Why did this work???

Well, the way in which you scrape the wire is very important. A torque is created which forces the wire to rotate when current (from the magnetic field) pushed the 'current carrying wire' perpendicularly. One side makes the wire turn halfway, and the other side finishes the cycle. 

Unit 6 Blogpost Summary

UNIT - ELECTRICITY

In unit 6, we learned all about  Electricity!  The sub-topics we focused on were .......

• Charges/Polarization (Coulomb’s Law)

• Electric Fields

• Electric Potential/Electric Potential difference (capacitors)

• Ohm’s Law & Electric Potential difference

• Types of current 

• Parallel and series circuits

Charges and Polarization including Coulomb's law —>

The first topic that we focused on in this unit was Charges and polarization. I thought that 'charge' was just the thing you did to your phone when it ran out of battery before this topic! In actuality, something becomes charged by having an extra amount or a lesser amount of protons or electrons (making it a negative or positive charge). The way that these objects become charged is through polarization. Something can become polar by friction or induction. An example of this is when you rub a balloon against your head and then attempt to stick it against the wall. I will give you an example of the correct way to answer this question fully 

1) The balloon is charged by friction when it is rubbed against your head. When it is brought towards the wall, the wall polarizes. This means that all of the positive charges in the wall are drawn towars the negative charges in the balloon.

2) The positive charges in the wall move as close to the balloon as possible while all of the negative charges in the wall move away from the balloon

3) The distance between the opposite charges (attractive) is smaller than the distance between the like charges (repulsive).

4) F = kq1q1 / d2 : (Coulomb's Law) Since there is a greater distance between the repulsive forces, the force between then will be less than the attractive forces. 

5) Therefore, the balloon will stick to the wall! 

6) d F     V.S.      d   F

Electric Fields  ---> 

An electric field is defined as, "a region around a charged particle or object within a force would be exerted on other charged particles or others". This section was fairly straight-forward. We learned that if the arrows are pointing outwards on an electric field, the inside charge must be positive and that if the arrows were pointing inwards, the charge must be negative. The best problem that we used to justify electric fields was .... "Why is your computer safe inside a metal box?"

ANSWER:

We put out devices inside of a metal box to protect them from getting an electric shock and breaking. Charges build up on the corners of objects and if the object were to come in contact with something that could give it a shock, the wires and everything in it would get fried and it would be useless. When it is placed inside a metal box, it is safe. This is because when the charges land on the metal box, the metal displaces them and they all become neutral, keeping the device from having a charge and possible breaking

Electric Potential/Electric Potential difference (capacitors) --->

Electric potential/electric potential difference was all to do with volt/voltage/and flash inside of a camera. Most people get confused between the difference of a volt and voltage..... 

VOLT= electric potential ( PE/q or J/C )

VOLTAGE = the difference in electric potential. Voltage causes current. 

ELECTRIC POTENTIAL = potential energy/charge

ELECTRIC POTENTIAL ENERGY = the stored energy between electric charges in electric fields

A flash is an example of a capacitor. Explain why you can’t use your flash continuously and by doing so explain how capacitors work

A camera has 2 oppositely charged plates inside of it. These two plates and not connected. You add charges to each plate thus increasing the Force and energy of the electric field between the plates. WHen you briefly connect the plates (push the button on your camera to take a picture) energy rushes from one plate to the next and a light in produced (flash). You cannot use flash continuously because you need to give the charges time to build up enough to create light.

Ohm’s Law & Electric Potential difference --->

"Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points." In our class, we learned that ohm's law deals with the relation to distance and we used the formula F = kq1q2/d2. The question of, "Why are the wingspans of birds a consideration in determining the spacing between parallel wires in power lines?" is a good one to help fully understand electric potential difference.

ANSWER:

When a bird lands on a wire, it does not get a shock because it is not completing a full circuit. Power-line-maker people are technically not allowed to put power lines close enough together so that a bird would be able to touch both of them. Two power lines next to each other would have a huge difference in voltage. Therefore, if a bird were you touch one line with one wing, and another line with its other wing, it would complete a circuit and a current would run through the bird. This could be detrimental to the bird, very likely causing it to die.

This is also the section where we learned about resistance and the formula for it. To calculate resistance we use I = V/R. So in a question like "You plug a 4A radio into a 240V circuit. What is the resistance of the radio?" we would answer it like this

4 = 240v / R

Multiply both sides by R

4R = 240

Divide both sides by 4

R= 60 ohms of resistance (Ω)

Types of Current, source of electrons, Power --->

There are two types of current, alternating current (AC) and direct current (DC). *We learned a pretty cool dance in class for this, you can see me after class if you want to see it*

Parallel and series circuits --->

There are two types of circuits that we focused on in this section. We learned that each circuit reacts very differently. 

Series : 

• When more appliances are added to the series circuit, the total resistance goes up. 
• When more appliances are added to the series circuit, the total current goes down.
• When more appliances are added to the series circuit, the total brightness goes down.
• When one of the lightbulbs is removed or stops working, the entire system of lightbulbs will go out

Parallel : 

• When more appliances are added to the series circuit, the total resistance goes down.
• When more appliances are added to the series circuit, the total current goes up.
• When more appliances are added to the series circuit, the total brightness stays the same
• When one of the lightbulbs is removed or stops working, the rest of the system and lightbulbs stay on

Mousetrap Car Reflection

Mousetrap Car

In this blog-post I will be explaining the Physics behind my mousetrap car and how the final product came out!

1. It took my car 4.65 seconds to go 5m. It ended up in 5th place in my class

2 and 3. Below is a picture of Dylan and I holding our car. I have added labels to the vital and most visible parts of our car.

4. If you want to see our car race in action, watch the video below!! 

5. I will now go into more detail about the actual creation of our car and how each step had physics properties involved in it.

Physics Behind the Mousetrap Car

A) Each of Newton's three laws can be applied to the mousetrap car. I will list each one.

NEWTONS 1st LAW : Newton's first law states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an outside force." Therefore, in this case, when we set the mousetrap and let it release, the car will want to continue to move until something else stops it. This 'something else' could be air particles, the frictions between the wheel and the ground, or even the wall (if you car does not go perfectly straight like mine). Although in this experiment, friction is the real and most common enemy. 

NEWTONS 2nd LAW : Newton's second law states that "Acceleration is produced when a force acts on a mass." This means that as the mass increases, you will need a greater amount of force to accelerate the object. If you remember, the formula for acceleration is acceleration = force / mass. This means that for every extra piece that we added on to our car, we were going to need a greater force to accelerate it. We tried to avoid having such a large mass by using the knitting needles as the main part of the car instead of a block of wood or something heavy. We knew that by having a light car, we wouldn't need such a strong force to give us an ample acceleration. 

NEWTONS 3rd LAW : Newton's third law states that "For every action, there is an equal and opposite re-action". For every action that occurs (lets say you pushing your friend) there is an equal and opposite re-action (meaning theoretically when you push your friend, they are pushing back against you with the exact amount of force that you exerted on them.) A perfect example to explain equal and opposite forces is the example of the horse and buggy. If you do not remember this example, I will quickly explain it again.

Horse and buggy- First of all, there is the force of the horse pulling on the buggy and the buggy pulling back on the horse. This creates an action and reaction pair and the forces and both equal and opposite. Then there is the horse pushing the ground back and the ground pushing the horse forward. This is also an action & reaction pair of equal and opposite forces. The last set of action and reaction pairs is between the buggy pushing the earth forward and the earth pushing the buggy backwards. There is one thing you have to remember about the horse/ground reaction and the buggy/ground reaction. In order for the buggy to be moving (which in this case, let's say that it is), the arrows that you draw between the horse and the ground when making a diagram must be bigger than the set of arrows between the buggy and the ground.

There are multiple action/reaction pairs in my mousetrap car, but the main one that I think is most important to mention is the forces between the wheels and the ground. The wheels push the ground backwards while the ground pushes the car forward. 

B) This is the main reason why we need friction between the ground and the wheels of our car. We attempted to create more friction but wrapping the plastic lining of a balloon around each of the wheels. This is one of the ways to increase friction. The other way, which I did not consider until out class discussion, is that you can increase friction by simply increasing the weight of the car. Although, you have to be careful with how much mass you add on to the car because if it becomes too heavy, like I said earlier, you will need a much larger force to accelerate it which may not be able to be achieved when the weight gets to a certain intensity. 

C) I think that the size of the wheels on my mousetrap car were a great advantage to me. We used four, standard CD's for our wheels. Like many parts to this project, you had to find the right balance with the size of the wheels. This all ties in with torque, force and lever arm. If you put HUGE wheels on your car (like the size of records) you would have a HUGE torque, but you would need so much more rotational inertia in order to get the wheels to move. Oppositely, if you had very small wheels (like ones taken off of a toy car) you would barely need any rotational inertia to get them to move, but the torque would be super small. You have to find the right balance between all of these challenges. There were a few surprises that I learned from discussing the mousetrap car in class, after we raced them. I learned that the car will always have the same torque regardless of the size of the lever arm. This can be very misleading because we know that when you increase the lever arm, you require a smaller force and when you shorten the level arm, you need a larger force. So, while the lever arm does not affect the torque of the car, it DOES make the distance larger. Just like in previous cases, you have to find a balance between the length of the lever arm and the amount of force used to maintain that constant torque. 

D) There is a lot of Potential and Kinetic energy in our mousetrap cars. When you wrap the string around the axle generating potential energy. Whatever amount of potential energy the string has will be the maximum amount of kinetic energy it can turn into. Once you release the mouse trap and the string pulls the axle forward, that potential energy is transformed into kinetic energy. Some things that you DO NOT want in your car is wobbly wheels. This WASTES ENERGY!! It was funny to hear other groups exclaim that they could only get their car to go in a circle (although i'm sure this was very frustrating for the students). We learned that this is because when the wheels are slanting inwards, there is a centripetal force, JUST LIKE what we learned in that unit when a race car is attracted to the center of the track when it goes on the ramps. If you are trying to win a race in the straight, forward direction, you do NOT want a centripetal force. 
E) Rotational inertia, rotational velocity and tangential velocity played a large role in the wheels of our mousetrap car. The larger that your wheels are, the lower the rotational velocity will be. Meaning that oppositely, if you have very small wheels, you will have a great rotational velocity. The key was to find the perfect size of a wheel that the rotational inertia and rotational velocity coincided well and gave you a fast car. Larger wheels are much harder to spin and take more effort to complete a full rotation, but smaller wheels (while quicker to rotate) have to spin many more times which can result in a loss of energy. The tangential velocity is just the actual speed that the wheels cause the car to turn at. If you were lucky, you had a steady tangential velocity because you balanced out your rotational inertia and rotational velocity. 
F) When looking at our mousetrap cars, we realize something extremely surprising! We cannot calculate the amount of work that the string does when it pulls on the axle and consequently, causes the wheels to rotate and propels the car forward. This is because the force and distance are not parallel and we just recently learned that if the force and distance in an object are in perpendicular directions, we will not be able to calculate the work done. 

Reflection

A) The final design of our mousetrap car was extremely similar to our primary sketches. I think that we were very practical when deciding what materials we would use so there were not a bunch of drastic changes to our original thoughts.
B) The one main problem we had with our car was trying to get it to go straight. When attaching the wheels I suppose we should have been more precise about gluing them on securely so that they were facing directly forward. We attempted to overcome this issue by rearranging the already glued-in-place wheels, which was extremely difficult. Finally, even though we were not able to get the car to go perfectly straight, the wheels were fixed enough and we started the car at the right angle so that we were able to make it over the 5m mark.
C) If I was to do this project again, I would overall be more precise with my cutting and gluing because I think that every extra moment of care helps. One of the main things I would try to change it the friction of my wheels and the lever arm. heil I do need a certain length of lever arm to get the car to cross the set distance, I would experiment with the length and weight of it to try and have it go as fast as possible. 
D) If I were to do ANOTHER building process, I would remind myself that hard work always pays off. When planning, I would come up with a backup plan for when things did not go the way you had expected them to. I would plan out my goal and my plan if the goal was not completed because it was very stressful as the due date approached and we were still struggling to put the final touches on our car when I assumed that we would be done with ample time. Overall, I would try to maintain a good attitude like I did in this building project because it was genuinely a lot of fun. 

UNIT 5 SUMMARY

A) In this unit I learned about...

• Work and Power
• The Relationship between Work and Kinetic Energy
• Conservation of Energy
• Machines

Work & Power

Work is something that occurs every time there is a certain Force and Distance that are parallel to each other. We can express this in the formula, Work = F • d. An example of this would be walking up the stairs. Your force, lets say 600N, multiplied by the height of the stairs, maybe 10m, would give you the amount of work you have done. 600N * 10m = 6000J. The J stands for Joules (Work is measured in Joules).

WORK IS NOT DONE IF..... 

1) THE FORCES ARE NOT PARALLEL 

2) NO DISTANCE IS COVERED

Work is responsible for power. If I wanted to know how much power it took for me to run up the stairs there are two things we need to know. To find power, we need to know our work and the time it took us to do that work. The formula for power is, Power = Work / Time. So, if we think back to someone walking up the stairs, we can guess that it took that person about 10s to get to the top of the staircase. Our equation would come out like this..... 6000J / 10s = 10 watts. (Power is measured in watts). 

FUN FACT: There are about 746 watts in 1 horsepower. The average truck engine has a horsepower of roughly 320..... (thats a lot!)

The Relationship between Work and Kinetic Energy

The formula for Kinetic Energy is KE = 1/2 m (v) ². The word 'energy' comes from the Greek word 'energon'. It translates literally to = 'I have work in me.' But, if we put this is simpler terms, it is the ability to do work. Kinetic also comes from the Greeks. 'Kinema' means = movement. So, if we combine the two, we get 'the energy of movement.' Energy is also measured in Joules. 

You might see a question about the relationship between Work and Kinetic Energy formulated like this....

1) A 20kg car accelerated from 20m/s to 30m/s over a time span of 5 seconds. In that time, it traveled 100 meters. 

a) What was the change in energy that the car experienced?

KE = 1/2 m (v) ² 

∆KE = Kfinal - Kinitial

KE initial = 1/2 (20)(20)²

= 4000 J

KE final = 1/2 (20)(30)²

= 9000 J

9000 - 4000

= 5000J

b) How much work was done?

Work = ∆KE 

Work = 5000J

c) Calculate the force the car used that caused the car to accelerate?

Work = F • d 

5000J / 100 = F • (100) / 100

F = 50N

d) What was the power during the acceleration?

Power = Work / Time

Power = 5000 / 5

= 1000 watts

Then, of course, we have our HUGE point question. The question is.... 

In terms of work and energy, why do airbags keep us safe? 

KE = 1/2 m (v) ² : You are going to go from moving to not moving regardless of what stops you.

∆KE = Kfinal - Kinitial : Your ∆KE is going to be the same regardless of what surface you hit.

Work = F • d : With an airbag, you are increasing your distance and therefore lessening your force. This is because the force is being applied in smaller increments over a longer period of time. 

So..... 

WITH AIRBAG = F • d

WITHOUT AIRBAG = F • d

Conservation of Energy

Conservation of Energy incorporates Potential Energy into the equation. The formula for Potential Energy is Mass • Gravity • Height. (PE = mgh) Potential energy is also measured in Joules. The relationship between potential energy and kinetic energy is that potential energy = the kinetic energy at its lowest point (and vice-versa). While something CAN be moving and have potential energy, it is IMPOSSIBLE for something to be at rest and have kinetic energy. (Kinetic energy relies on movement and it cannot be present if the velocity is zero!!) The law of conservation of energy tells us that energy cannot be created nor destroyed. It can only be transformed into different forms. 

So, if you weigh 50kg and you jump off of a swing-set that was 5 meters high, your potential energy would be....

PE = mgh

(50) (10) (5)

= (500) (5)

= 2,500 J

This means that at the top of the swingset, my potential energy is 2,500 J and my kinetic energy is 0 J. I can bet that you already know that just before I hit the ground my potential energy will be 0 J and my kinetic energy will be 2,500 J. 

Another way to remember this is with a roller coaster. Have you ever wondered why you keep going forward, up and down the huge hills? Well, as long as all of the hills are smaller than the initial one, you should be able to get over them. We can prove this because we know that energy cannot be created or destroyed, only transformed.

Machines

The job of a machine is to decrease the amount of force you have to use (all at once) by increasing the distance. In this subject we focus on work-in and work-out. Work-in = Work-out. An example of a simple machine is a ramp. We put 'work-in' on the ramp, and get 'work-out' at the top. Another formula presents itself at this time. When talking about work, we want to know the efficiency we are completing this work at. Efficiency = workin / workout. There is hardly any machine in the world that has an efficiency rate of 100%. This is due to lost energy in 3 different forms. These are heat, light, and sound. 

If you are trying to push a heavy box (500N) up a ramp and into a truck, how much force are you actually putting in, with the help of your machine? (The ramp is 10m high and 10m long)

Workin = Workout

F-in • d-in = F-out • d-out

F • (10) / 10 = 500 • 10 /10

F = 500N

THANKS FOR READING!

I HOPE YOU LEARNED A LOT!