# A pendulum on some moon has a length of 1.5meters and a period of

1. Jan 4, 2012

### TutorGirl22

A pendulum on some moon has a length of 1.5meters and a period of 4.2seconds. On earth a girl throws a rock 13meters in the air, if she was on that moon how high would that same rock go if she threw it with the same effect? (Ignore all air resistance)

2. Jan 4, 2012

### rollcast

Re: Pendulum

T=2$\pi$$\sqrt{\frac{L}{g}}$

g=$\frac{4\pi^{2}L}{T^{2}}$

g=$\frac{4\pi^{2}1.5}{4.2^{2}}$

g= 3.3570083m/s2

3. Jan 4, 2012

### TutorGirl22

Re: Pendulum

I found the gravity okay, it was the next part that I got hung up on.

4. Jan 4, 2012

### rollcast

Re: Pendulum

Can you work out the initial velocity for the rock on the earth?

5. Jan 4, 2012

### TutorGirl22

Re: Pendulum

That's the train of thought that I had, but I don't know how I would do that.

6. Jan 4, 2012

### rollcast

Re: Pendulum

Think of the SUVAT equations, you know,

S = 13m
U = ?
V = 0 as at the maximum height the velocity will be zero
A = g for Earth

T doesn't matter

Which SUVAT equation has those 4 variables in it - SUVA ?