# Pls. help -> acceleration

1. Aug 20, 2007

### mayeh

pls. help --> acceleration

1. The problem statement, all variables and given/known data
a ball starts from rest and rolls down a hill with a uniform acceleration travelling 150m during the second 5.0s of its motion. How far did it roll during the first 5.0s of its motion

pls. help

2. Relevant equations

3. The attempt at a solution

2. Aug 20, 2007

### ron_jay

what have u tried so far so that we can help u?

3. Aug 20, 2007

### mayeh

i tried to get its acceleration and i got a 3m/s^2, but after that i dont know what to do, I'm not even sure if i got it right.

4. Aug 20, 2007

### ron_jay

What you have to see first is that the distance travelled by the rolling ball in the next 5 seconds is nothing but the difference between the distance travelled by the ball in 10 seconds and the distance travelled in 5 seconds.

By the simple kinematic equation, we know that:

S=ut+(1/2)at^2

Since the initial velocity u is 0, the ut component of the equation goes and only (1/2)at^2 is left.So the distance travelled in the next 5 seconds is nothing but:

(1/2)a{(10^2)-(5^2)}=150

Solve for 'a'.(It wouldn't work out to 3m/s^2.)
Now, u know 'a' so substitute it in the equation (1/2)a.5^2 to get the answer!