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Conservation of mechanical energy of ball of mass

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1. Homework Statement
A ball of mass 240 g is moving through the air at 20.0m/s with a gravitational potential energy of 70J. With what speed will the ball hit the ground?

2. Homework Equations
Eg = mgh
Ek = 1/2mv^2
W = mgd

3. The Attempt at a Solution
this is what i did:
at 0m, potential energy is 0 so kinetic energy must have 70J now.

Ek = 1/2mv^2
70 J = 1/2(0.24kg)v^2
v = 24.15 m/s

I dont know what to do with the 20 m/s that was given and yeah....please help!

Answers and Replies

The potential and kinetic energy that it had initially is now all kinetic by the time it reaches the ground.
you have

potential energy + kinetic energy = total energy = constant

What is the total energy whe the ball is moving through the air? it's not 70 J.

At a height of 0 m, potential energy is indeed 0, so all the energy must be kinetic.
since he total mechanical energy is conserved equate the initial total mechanical energy
(pe+ke)to the final toal mechanical enrgy.
remeber pe=mgh ,so what is pe at ground level?