# Math Help - Mechanics: Potential energy

1. ## Mechanics: Potential energy

Very basic but i don't understand it...
A particle of mass 2kg falls freely from rest. Calculate kinetic energy when it has descended 20 meters.
Answer is 392J and i get 392000J.

But i just did 2000(weight) x 9.8(gravity) x 20(distance)
And i think thats wrong...well it must be because the answer i have is wrong lol.

2. Hi

The weight must be expressed in kg and not in g
BTW gravity is 9.8 N/kg ...

3. Originally Posted by running-gag
Hi

The weight must be expressed in kg and not in g
BTW gravity is 9.8 N/kg ...
tyvm

4. Originally Posted by AshleyT
Very basic but i don't understand it...

Answer is 392J and i get 392000J.

But i just did 2000(weight) x 9.8(gravity) x 20(distance)
And i think thats wrong...well it must be because the answer i have is wrong lol.