Rotational Motion review
Directions: Show your work.  Show the correct units.  Get the correct answers.

If the torque required to loosen a nut on the wheel of a car has a magnitude of 40.0 N m, what is the minimum force that must be exerted at the end of a 30.0 cm wrench to loosen the nut? (Donít forget to convert!)
 
 
 
 
 
 

How (and why!) would the force required to open the classroom door change if you moved the handle from its present position to the middle of the door?
 
 
 
 
 
 

Give three examples of objects that have no mass at their center of mass.
 
 
 

A 400.0 N child and a 300.0 N child sit on either end of a 2.0 m long seesaw.  Where along the seesaw should the pivot (fulcrum) be placed to ensure rotational equilibrium?
 
 
 
 
 

Why would be advantageous to have a low center of mass as a bicycle rider rounds a turn?
 
 
 
 

Two children are rolling automobile tires down a hill.  One child claims that the tire will roll faster is one of them curls up in the tireís center.  The other child claims that will cause the tire to roll more slowly.  Explain which is correct using the concept of moment of inertia.
 
 
 
 
 

As Halleyís comet orbits the sun, its distance from the sun changes dramatically, from 8.8 x 10^10 m to 5.2 x 10^12 m.  If the cometís speed at closest approach is 5.4 x 10^4 m/s, what is its speed when it is farthest from the sun if angular momentum is conserved?
 
 
 
 
 

Why is the moment of inertia of a tether ball swinging on a rope greater than spinning a stick of equal mass around?  (In other words, why are the formulas different for the two objects?)
 
 
 
 

Give an example (in words or pictures) of a tool (or tools) that incorporate each of the following simple machines.
Lever
Inclined plane
Wheel and axle
Wedge
Pulleys
Screw
 

Letís say you are using a crowbar to pry open a sealed wooden chest.  It takes 550 N of force at the tip of the crowbar to break it open when the tip is 0.05 m from the fulcrum.  If you had your hands 0.95 m from the fulcrum, how much force did you need to use to get to the treasure?
 
 
 


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