In an experiment, a student is releasing a block from the top of several distinct inclined planes and allowing it to slide to the bottom. Assume that the tracks are frictionless and that all inclines have equal heights. The speed of the block at the bottom will maximized if the angle of incline is closest to:
A. 90º.
B. 45º.
C. 0º.
D. The angle of incline is irrelevant.
Click for Explanation
This is a conservation of energy question. The block begins with only gravitational potential energy. When reaching the ground, all of that energy has been converted to kinetic energy. Because the block is starting with the same mass and the same height, it will therefore start and end with the same total energy. Thus it will have the same speed upon reaching the ground, regardless of the angle of inclination.
Note that the block is never released from an incline with exactly 0º (flat ground), since the incline has some height and the question only says “closest to”, not “equals”. The answer is (D).
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