Question

You are holding ball at the height of 1.5 meters m = 2 kg h = 1.5 m You are holding a 2 kg ball at 1.5 meters. What is the mechanical energy at the 1.5 m height and what is the mechanical energy at 0, in other words what is the mechanical energy at release and what is the mechanical energy at impact. What is the velocity at the impact?

Answer 1

According to the law of conservation of energy total mechanical energy remains constant in the case of freely falling body.

The initial potential energy of a body at a height is E_P=mgh

= 2x9.8x1.5 =29.4J = E (release)

The final kinetic energy of the body at 0 is E_K =29.4J = E (impact)

Now the velocity with which it reached to the point 0 is v

Using the equation of motion $v^{2}-u^{2}=2as$

Here s= h = 1.5m

u= 0 initial velocity

v= final velocity which is to be determined

a= g =9.8m/s² , acceleration due to gravity

Now v² -0 = 2x9.8x1.5= 29.4

v² =29.4

This is velocity of impact v = 5.42m/s