Question

Question # 40

A body falls freely under gravity. If speeds is v when it has lost an amount x of the gravitational P.E, then its mass is:

2x / v2
2x / v3
2x / v4
none
please give me its solution

Answer 1

Potential Energy = x = m g h

Kinetic energy = 1/2 m v^2

Assuming the mass fall from rest

1/2 m v^2 = m g h

v^2 = 2 g h

So the speed attained is independent of the mass

Also, x / v does not have the units of mass

So the solution is none of the above.