Torque & Machines Test
Directions: Show your work.  Show your units.  Get the correct answers.

Name the simple machine exemplified by each thing:

Razor blade ____________________

Winch  ____________________

Spiral stairs ____________________

A bolt  ____________________

Axe  ____________________

Tongs  ____________________

Pair of pliers ____________________

Wench  ____________________
 

A 15,000N car needs to be moved to the back of a truck 5 m above its initial location.  Calculate the mechanical advantage if 4,000N is applied to a cart to push it up a 20 m ramp.
 
 
 
 
 
 

What is the efficiency of the system above?
 
 
 
 

A rope is wound around the crank of a lawn mower.  The crank has a radius of 0.30 m. To start the mower, the lawn boy exerts a force of 70N on it. What is the torque exerted by the lawn boy?
 
 
 
 
 

How much force is required to press down on a pair of bolt cutters 0.64 m from the fulcrum if 400 N of force is required to cut a hardened steel lock 0.07 m from the fulcrum?
 
 
 
 
 
 

Which moment of inertia equation would you use for each of the following?

Swinging a ball on a chain  __________________

Swinging a baseball bat   __________________

Rolling a hulla hoop down an incline __________________

Rolling a basketball down the court __________________
 

Tell if the following objects have rotational equilibrium (R), translational equilibrium (T), both (B), or neither (N)
_____ A  boat propeller, spinning at a constant velocity as the boat accelerates in the water.
_____ A fence post.
_____ A building.
_____ An asteroid traveling at a constant speed through space, while turning on its axis at a constant rate.

Compare two cylinders of equal mass and diameter. One is solid the other is hollow. Which would accelerate faster?  Explain why in complete sentences.
 
 
 
 
 
 

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? (Answer both questions (i.e., “how” and “why” in complete sentences.)
 
 
 
 
 
 

Useful formulas:
T = F x l   MA = Fout / Fin   Efficiency = W out / W in
W = F x d  Moment of Inertia: Check your notes


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