Whats the velocity of a ball falling with 100joules of kinetic energy and a mass of 2 kilograms?

Short answer: v = 10 m/s

Comment

This is just an application of KE = 1/2 m v^2

Givens

KE = 100 Joules

m = 2 kg

v = ?

Formula

KE = 1/2 m v^2

Substitution and Solve

100 = 1/2 * 2 * v^2

100 = v^2 Take the square root of both sides.

sqrt (100) = sqrt (v^2)

v = 10 m/s

Comment

There is no KE unless v > 0.

You may have PE when v = 0, but not KE.