C) either of these 20) Which task requires more work? A) lifting the 50-kg sack 2 meters C) lifting the 25-kg sack 4 meters 21) A moving object has momentum. B) speed. C) velocity. D) energy. E) all of these 22) A circus diver drops from a high pole into water far below. When he is halfway down A) he has gained an amount of kinetic energy equal to half his initial potential energy. B) his potential energy is halved. C) his kinetic energy and potential energy are equal. D) all of the above E) none of the above 23) Neglecting air resistance, Sammy Smarts on a high ladder releases a ball that strikes the ground with 100 J of kinetic energy. If he were to instead throw the ball straight upward, it will soon reach the ground with a kinetic energy of B) more than 100 J. C) 100 J. A) less than 100 J. of ledenog via 3) both require the same D) need more information 24) When you and your snowboard are in motion, which of the following can be zero? A) inertia B) kinetic energy C) momentum D) mass E) none of the above 25) A ball is projected 125 meters straight upward and then falls the same distance back to its starting point. Neglecting air resistance, its total time in the air is about A) more than 20 s. B) 5 s. C) 15 s. A-3 10 s. 20) 21) a 23) 24) 25) -