# Change in momentum of a ball

1. Jan 2, 2010

### yamugushi

1. The problem statement, all variables and given/known data
A ball is rolled into a wall and bounces back at the same speed, the change in momentum is?

2. Relevant equations
Ein = Eout

3. The attempt at a solution
I thought it was m(v) but I got it wrong (doing test corrections ATM)

Note I'm having trouble editing, so I made a new thread, I am not trying to spam.

2. Jan 2, 2010

### rock.freak667

If the velocity before impact is v, what is the velocity after impact?

(remember, velocity is a vector quantity, so direction is important)

3. Jan 2, 2010

### yamugushi

So it's be -mv... but there aren't any negative answers:
I have
0
1.5
.5
2
and what I answered MV (all above are times MV as well)

4. Jan 2, 2010

### rock.freak667

So momentum before is mv, and momentum after is -mv, so that change in momentum is ?

5. Jan 2, 2010

2mv?

6. Jan 2, 2010

### rock.freak667

is that one of the answers?

7. Jan 2, 2010

0mv
1mv
1.5mv
.5mv
2mv

8. Jan 3, 2010

### Winzer

Just to note:

The original velocity must have been negative. The initial momentum was $$P_1=-mv$$.
Following the bounce, the final momentum is $$P_2=mv$$.