# Simple Gravity Problem

1. Jun 20, 2012

### gbaby370

I am doing a problem which involved determining how fast a rocket was launched off the earth to reach a maximum height.

I am looking for some assistance with some simple algebra.

The formula used is;

Etotal = -Gm1m2/r+0.5m2v^2

To isolate for v, would my equation be;

v=sqrt(2(Etotal+(Gm1/r))

2. Jun 20, 2012

### Staff: Mentor

OK.

Not exactly. (You missed an m2 in there.)

But instead of doing this, express the total mechanical energy at the highest point and compare it to that at the starting point. Then you can make use of energy conservation.

3. Jun 20, 2012

### gbaby370

I looked over it again and found the answer I was looking for.

4. Jun 20, 2012

### gbaby370

Ok so I rearranged and got the correct answer. I was just wondering if this equation I've attached can be reduced even further?

#### Attached Files:

• ###### Untitled1.png
File size:
4.2 KB
Views:
54
5. Jun 20, 2012

### Staff: Mentor

I would combine those fractions using a common denominator.

6. Jun 20, 2012

### gbaby370

Ok, how does this look?

#### Attached Files:

• ###### Untitled2.png
File size:
4.9 KB
Views:
47
7. Jun 20, 2012

### Staff: Mentor

Looks good to me. (You can even put the 2 in the numerator and erase one set of parentheses.)

8. Jun 20, 2012

### gbaby370

Oh ya?

Thanks for you help.