1. a rock is falling off a cliff. the work that gravity performs on the rock is a) zero b)positive c)negative 2. the sunlight that reaches earth is generated by a transformation of a) mechanical energy b) atmospheric energy c)chemical energy d)nuclear energy 3.at a department store, a toy train travels on a loop of track of length 14 m. the coefficient of rolling friction between the train's wheels and the track is 0.10, and the weight of the train is 65 n. how much work does the train do against friction during each trip around the loop? a) 91 j b) 180 j c) 41 j d) 0 j 4. a ball is released out a window that is 13 m above the ground. how fast will the ball be traveling when it reaches the ground? a) 0.26 km/s b) 0 m/s c) 16 m/s d) 32 m/s 5.a tennis ball is released from a height of 3.7 m above the floor, and then bounces three times. with each bounce, dissipative forces cause it to lose 18.0% of its mechanical energy. how high does it reach after the third bounce? a) 200 cm b) 20 cm c) 200 mm d) 250 cm 6.at a certain point on the trackway, a roller coaster car has 27,000 j of potential energy and 132,000 j of kinetic energy. the value 159,000 j equals of the coaster car at this point. a) the total mechanical energy minus dissipated energy b) the total mechanical energy plus dissipated energy c) the total mechanical energy d) the total internal and external energy 7.a car of mass 1290 kg is traveling along a horizontal road. during a span of 8.9 seconds, the car accelerates from 10.0 m/s to 16.5 m/s. how much work does the car's engine perform on the car during this time? a) 791 kj b) 340 kj c) 692 kj d) 111 kj