Unit 4 Summary

Unit 3 Summary

A) In this unit I learned about...

• Rotational & Tangential Velocity
• Rotational Inertia
• Conservation of Angular Momentum
• Torque
• Center of Mass/Gravity
• Centripetal & Centrifugal forces

Rotational & Tangential Velocity

Rotational and tangential velocity go hand in hand when we are talking about the speed/distance at which something rotates. Although, rotational and tangential velocity are two very different things. It is easiest to understand the difference between the two with an example..... 

If there are two people running a race on a track (one starts in lane 1 and the other in lane 7) who would win the race? Most of us would suspect that the person on the innermost part of the track would win... and this is correct! But do you know why? WELL, this all depends on the rotational & tangential velocity of the runners. The person on the inside has a much smaller distance to cover per lap, therefore they will have a much faster rotational velocity (meaning that they will be making full rotations at a much faster rate than the person on the outermost lane). The person on the outside could be running faster (giving them a faster tangential velocity which is their actual speed) but it will be extremely difficult for them to run fast enough to surpass the person running on the inside. 

So.... Rotational Velocity= speed of one's RPM (rotations per minute)

& .... Tangential Velocity= the speed tangential to the center of rotation at any point (actual speed)

Rotational Inertia & Angular Momentum

Rotational Inertia has to do with how much an object is willing to rotate. If something has a high amount of rotational inertia it will be less likely to spin, while an object with very little rotational inertia will be more willing to rotate. There is a major factor that determines whether or not something will have a high or low rotational inertia is where the mass is located. If the majority of the mass is near the center of rotation, the object will more fast meaning that it has less rotational inertia. If the mass is displaced further away from the center of rotation, it will rotate slower giving it a higher rotational inertia. An example of this is with a basketball and a bowling ball. The bowling ball will roll down an inclined plane faster because more of the mass is closer to the center of rotation. Angular momentum is a counterpart to rotational inertia. It is the product of rotational inertia * rotational velocity.

Torque

Torque is what causes rotation. An object needs two things to have a torque. This is a force and a lever arm. A lever arm is the distance from the axis of rotation and the force is the force that is being applied on the object in order for it to want to rotate. We have to remember the counterclockwise torque is = to clockwise torque. This means that their lever arm and force will end up being balanced. You can get a large torque from having a 1) BIG force, 2) BIG lever arm, or 3) BOTH. An example of torque is when you are trying to un-twist a bolt with a wrench. You have to exert a certain amount of force that balances out the lever arm resulting in a torque!

Center of Mass/Gravity

Center of Mass and Gravity the the topic that I had for my podcast. The short clip above will explain the difference between center of mass and gravity and give a good example of how wrestling is applied to this concept.

Centripetal & Centrifugal Forces

FIRST OF ALL, I would like to start by making if very clear that centrifugal force is not a real thing.

Now that we have covered that, I will explain centripetal force. Centripetal force is a force that attracts objects inwards (to the center). A most basic and easily visualized example of this is the earth's pull on the moon. As the moon orbits the earth, there is a certain amount of inward pull that the earth exerts on the moon. This is centripetal force. Centripetal force is also present when you make a sharp turn in a car. Centripetal force has a little something to do with our old friend inertia. A fun fact = if at any point the centripetal force disappeared, the moon would continue moving perpendicular to the force that had been pulling on it. 

B) This unit connects with our everyday lives pretty well. Every example we dealt with, (whether is was our earth and moon's forces or trying to unhinge a screw with a wrench), the event is an everyday occurrence. I think that this factor helps especially when trying to understand Unit 4 as a whole. I hope this blog post has cleared up some confusing topics for you and good luck on your next assignment regarding this information!