Question

Which of the following properties of a ball is conserved as it falls freely in a vacuum?
kinetic energy
gravitational potential energy
monentum
mechanical energy

Answer 1

Hi! Do you have any thoughts?

Answer 2

Any guesses?

Answer 3

D

Answer 4

yea cken .. what do you think? do you have any idea?

Answer 5

The mechanical energy is conserved whenever the force acting on the object is conservative - the gravitational force is a conservative one. so the mechanical energy in the case of a free fall would be conserved.

Momentum is meaningless here for a free fall. but we can only say that time rate of change of momentum near the ground is, with a good degree of accuracy, conserved. For a head-on collision it is conserved. see below

The same thing is held for gravitational potential energy, but instead of time rate we have displacement rate. see this:


the kinetic energy varies with the velocity. it is only conserved whenever we are moving on a surface of constant gravitational field.

I hope it makes sense :)