Question

a 500g one is thrown up with a velocity of 15m/s find its
(1) potential energy at its max height
(2) kinetic energy when it hits the ground

Answer 1

Answer:

Both answers will be 56.25 J

Explanation:

We know that the maximum potential energy (when the ball is at it's maximum height) is equal to the kinetic energy when the ball is released, as according to the law of conservation of energy, the initial kinetic energy, will be converted into potential energy. Hence, we don't need to know height to solve (1).

Solution for (1):

=> potential energy = initial kinetic energy

                                 = 1/2 . m.v^2

Given velocity(v) = 15m/s and mass in kg = 0.5kg

                                 = 1/2. 0.5.15^2

                                 = 56.56 J

Solution for (2):

Again, according to the law of conservation of energy, energy neither gets created nor destroyed, but only transformed from one form to another. In this case, maximum potential energy, gets converted back into kinetic energy. Hence kinetic energy when it hits the ground is also, 56.25J.

I hope the answers are correct!