A jack system will increase the potential energy of a heavy load ...

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A jack system will increase the potential energy of a heavy load by no more than 1000 J with a work input of 2000 J. The efficiency of the jack system is at most
 
  A) 10.
  B) 20.
  C) 50.
  D) 80.
  E) not enough information

Question 2

A heavy stone and a light stone are released from rest in such a way that the amount of gravitational potential energy of the system rock-Earth for each rock is the same just as they are released. Air resistance is negligibly small.
 
  Which of the following statements about these stones are correct? (There could be more than one correct choice.) A) The initial height of the light stone is greater than the initial height of the heavy stone.
  B) The stones must have been released from the same height.
  C) The stones both have the same speed just as they reach the ground.
  D) Just as it reaches the ground, the light stone is traveling faster than the heavy stone.
  E) The stones both have the same kinetic energy just as they reach the ground.

[tsternbergh47]

Answer to Question 1

Answer: C

Answer to Question 2

A, D, E

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[tsternbergh47]

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