Work Energy

Zero kinetic energy occurs when . . .

• 
  

  a moving object falls to the Earth.

• speed reaches zero.

  
  

• 
  

  speed increases.

• 
  

  speed is constant but mass doubles.

A force does work on an object if a component of the force

• 
  

  is parallel to the displacement of the object.

  
  

• parallel to the displacement of the object moves the object along a path that returns the object to its starting position.

  
  

• 
  

  perpendicular to the displacement of the object moves the object along a path that returns the object to its starting position.

• 
  

  is perpendicular to the displacement of the object.

A boy pushes on a parked car with a force of 200 N. The car does not move. How much work does the boy do on the car?

• 
  

  zero

  
  

• 200 N

• 200 J

• can't be determined

The law of conservation of energy states that . . .

• 
  

  the energy of a system can disappear.

• 
  

  energy cannot change form.

• 
  

  it is impossible to make a perpetual motion machine.

• 
  

  energy can neither be created nor destroyed.

  
  

What happens to the total amount of energy during an energy conversion?

• 
  

  no friction.

• 
  

  very little loss or gain of energy.

• 
  

  energy loss due to heat.

• 
  

  no loss or gain of energy.

  
  

A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work done on the ice-cream cone?

• 
  

  0.5 J

• 
  

  2 J

  
  

• 
  

  20 J

• 0 J

Describe the relationship between force and motion for work to be done.

• the applied force must be perpendicular to the direction of motion

• 
  

  the applied force must be opposite to the direction of motion

• 
  

  motion must be perpendicular to the direction of the applied force.

• 
  

  the applied force must be the same as the direction of motion

CALCULATIONS REQUIRED. The brakes on a car exert a frictional force of 6000N in getting the car to stop. If the work done by the brakes is 400000J in coming to a stop, how many meters did the car travel after the driver applied the brakes?

• 33 m

• 
  

  22 m

• 
  

  67 m

• 133 m

Answer explanation

Fuck the calculation. Just memorize answer

Car J moves twice as fast as car K, and car J has half the mass of car K.  The kinetic energy of car J, compared to car K is

• 
  

  1 to 2.

• the same.

• 
  

  2 to 1.

  
  

• 4 to 1.

If you push twice as hard against a stationary brick wall, the amount of work you do

• 
  

  remains constant but non-zero.

• remains constant at zero.

  
  

• doubles.

• 
  

  is cut in half.