If a 0.15 kg ball falls and has a ke of 20 j just before striking the ground, from what height did it fall. a. 1.36m b. 3m c. 13.6m d. 30m

According to the conservation of mechanical energy, the kinetic energy just before the ball strikes the ground is equal to the potential energy just before it fell. 

Therefore, we can say KE = PE
We know that PE = m·g·h

Which means KE = m·g·h

We can solve for h:

h = KE / m·g
   = 20 / (0.15 · 9.8) 
   = 13.6m

The correct answer is: the ball has fallen from a height of 13.6m.

An atom that has fewer electrons that protons is called a positive ion.