Posted by **Jessica** on Friday, February 17, 2012 at 11:06am.

A 3-kg stone is dropped from a height of 100 m. Find its kinetic and potential energies when it is 50 m from the ground.

- Physical Science -
**Henry**, Saturday, February 18, 2012 at 7:52pm
PE = mgh = 3 * 9.8 * 100 = 2940 J.

Vf^2 = Vo^2 + 2g*d,

Vf^2 = 0 + 19.6*50 = 980,

Vf = 31.3 m/s.

KE = 0.5m*V2 = 1.5*(31.3)^2 = 1470 J.

PE = 2940 - 1470 = 1470 Joules.

- Physical Science -
**Jessica**, Sunday, February 19, 2012 at 12:43pm
Where did you get the 19.6 from?

Also what formula are you using? The Vf^2 = Vo^2 + 2g*d....i've never seen that before

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