Thread: 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.

Any help please?

Hi

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

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

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.

Any help please?

the unit of mass (not weight) is the kg not the gm, so that should be:

2(mass) x 9.8(gravity) x 20(distance)

CB