# GPE and KE correctness help

## Homework Statement

1) What is the GPE of a 2 kg block 5 meters above the floor?

2) Joe throws a 4 kg stone straight up and it reaches a height of 5 meters. What is its GPE at its highest point?

3) How high do you have to lift a 1 kg ball to give it 49 J of GPE?[/B]

4) What is the KE of a 4kg mass at 3 m/s?

5) What is the mass of an object that has 100J of KE when moving at 5 m/s?

## Homework Equations

Honestly, the only thing I understand is the GPE stuff, which I believe is to simply multiply the mass and height together. I'm not sure if KPE is just as simple.

## The Attempt at a Solution

1) 10J

2) I got 20J but it says "highest point" so I don't know if that requires a different formula.

3) Seems simple enough, I got 49 meters by dividing 49J by 1 kg.

4 and 5 and basically Kinetic energy in general is what I need help on.

haruspex
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1) 10J
2) I got 20J but it says "highest point" so I don't know if that requires a different formula.
Why would the GPE at the highest point follow a different law from the GPE at any other point?
4 and 5 and basically Kinetic energy in general is what I need help on.
You haven't been taught any equations for KE?