1. Initially, an object has KE = 88 J. Over a given interval, thenet work done on the object iszero.

Which statement about this interval is true?

		the object's final KE must be zero
		the object's final KE must be 88 J, but it could have had more or less KE during the interval
		more information is needed
		the object's KE must have been 88 J during the entire interval

1. A system initially has 393 kJ of kinetic energy and 528 kJ of potential energy. A nonconservative force does -179 kJ of work on the system. What is the final mechanical energy of the system, in kilojoules?

Including the correct algebraic sign, the final mechanical energy is _____ kJ.

1. A rope exerts a 790-N tension on a crate sliding across the floor. The tension is directed 71^o above the horizontal. How far must the box be dragged for the tension to do 2000 J of work on it?

1.7 m

9.2 m

5.9 m

3.3 m

7.8 m

1. A body initially hasE = +100 J of mechanical energy. A non-conservative force does a total of +40 J of work on it. All of the pairs of KE and PE below could represent its state afterwards, except one. Which pair of KE and PEcouldn't belong to this body after the work is done on it?

KE = 0 J, PE = 140 J

KE = 90 J, PE = 70 J

KE = 170 J, PE = -30 J

KE = 20 J, PE = 120 J