# Homework Help: Constant force of ball

1. Jan 3, 2008

### mortho

1. The problem statement, all variables and given/known data
A 5.00 kg ball strikes a wall with a velocity of 6.0 m/s to the left. The ball bounces off with a velocity of 5.0 m/s to the right. If the ball is in contact with the wall for 0.30 s, what is the constant force exerted on the ball by the wall?

2. Relevant equations

f=p/t

3. The attempt at a solution

Ok so i found p which i did mv or (5)(11) then plugged it to p/t and did 55/0.30 and got 183.3 N to the right...is that correct?

Thanks!

2. Jan 3, 2008

### rock.freak667

Initial momentum is 5*-6=-30 kgms^-1

Final momentum is 5*+5=+25kgms^-1

what is the change in momentum? how does newton's 2nd law apply?

3. Jan 3, 2008

### mortho

oh....so 5 **Net force on an object is equal to its rate change of momentum.

4. Jan 3, 2008

### mortho

but that's such a small number is that possible??

5. Jan 3, 2008

### rock.freak667

Yes

The change in momentum=Final-Initial=25-(-30)=55kgms^-1

and by newton's 2nd law:F=55/0.3

so you are correct.