A 0.5 kg object slides down a frictionless incline from rest. It starts at a height of 5 m above the ground. What is its kinetic energy when it reaches the ground? (Take g = 10 m/s^2)
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Correct answer
D. 25 J
Principle or equation
Conservation of mechanical energy: initial potential energy mgh is converted entirely into kinetic energy (since no friction).
Why this answer is correct
Initial PE = mgh = 0.5 * 10 * 5 = 25 J. At the ground, PE = 0, so KE = 25 J.
Example
A 2 kg object dropped from 10 m has KE = 2*10*10 = 200 J at ground.
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