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45.
(Assume no friction)  An initially stationary 10.0 kg cart then slides down the track to the right.  After passes over he second hill, it reaches a second valley.  How much kinetic energy does the cart have when it reaches height , h3 ?

A.   98.0 h3                     C.   98.0 (h1  -  h3)

B.  98.0 (h2 -  h3)           D.  98.0 (h1  -  h2)
      
The increase in kinetic energy is equal to the decrease in potential.  Since it is motionless at the beginning, the increase in kinetic energy is its total kinetic energy.

PE = mgh     thus  /\PE = mg/\h

KE = 10.0 kg x 9.80 m/s2 x (h1  -  h3)   The Correct Answer is C.