# Ball thrown vertically in air question?

1. Oct 11, 2009

### yamaha277

1. The problem statement, all variables and given/known data

a) A 2.0 kg ball is thrown vertically in the air with an inital velocity of 10.0 m/s. What is the height of the ball when the velocity is 5.0 m/s?

b) A 2.0 kg ball is thrown vertically in the air. The height of the ball when the velocity is 5.0 m/s is 6.07 m. What is the initial velocity of the ball?

2. Relevant equations

3. The attempt at a solution

the max height reached by a) is 5.10 m

I know how to find the max height reached by the ball with the initial velocity but can't figure out how to find the height at certain velocities.

2. Oct 11, 2009

### mgb_phys

Do you know "v^2 = u^2 + 2as" ?

3. Oct 11, 2009

### yamaha277

This?
(square of final velocity) = (square of initial velocity) + 2*acceleration* distance

Would your final velocity in a) be 5.0 m/s therefore solving for s?
If that is correct, i get 3.83 m

4. Oct 11, 2009

### mgb_phys

There are three standard equations of motion (see the sticky at the top of this thread)
You need to know them - and which to use depending which factors you know.

5. Oct 11, 2009

### yamaha277

I have those and got:

A) 3.83 m
B) 11.99 m/s

Does the seem right?