# Homework Help: Gravitational Field question

1. May 25, 2005

### MiniTank

I am having some difficulty with this question:
A satellite is in orbit around Earth at an altitude of 3700 km. How much must its speed increase, in km/h, to escape the Earth's force of gravity?

I'm stumped. Please help

2. May 25, 2005

### whozum

Whats Earth's escape velocity?
What velocity is it orbitting at if its at that altitude?

3. May 25, 2005

### MiniTank

Earth's escape velocity = 1.12 x 10^4 m/s
and the velocity at that altitude is what im having tourble with

4. May 25, 2005

### whozum

Find the gravitational potential energy at that altitude. What doy ou know about the satelite's KE if it remains at that point?

5. May 25, 2005

### MiniTank

i think i get what your saying ..

Ek = 1/2 |Eg|
$$\frac{1}{2}mv^2 = \frac{1}{2}\frac{GMm}{r}$$
$$v=\sqrt{\frac{GM}{r}}$$

after i find that .. do i subtract that velocity from the escape velocity of earth?

Last edited: May 25, 2005
6. May 25, 2005

### whozum

Fix your tex tags, slash them the other way, /tex

7. May 25, 2005

### whozum

You've got all youj need to solve the problem.

8. May 25, 2005

### MiniTank

alright thanks ... appreciate it

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