Calculating Impulse: Homework Solution

[LBP]

Homework Statement

A 0.060-kg handball is thrown straight toward a wall with a speed of 11 m/s. It rebounds straight backward at a speed of 8.6 m/s.

(c) The rebounding ball is caught by a player who brings it to rest. During the process, her hand moves back 0.40 m. What is the impulse received by the player?

(d) What average force was exerted on the player by the ball?

Homework Equations

P=MV
I=delta P= M(Vf-Vi)
Inet=(F_avg)(delta t)

X= X0 + V0t -1/2at^2
V=V0-at

The Attempt at a Solution

From parts A and B I know the impulse on the wall was 1.176 into the wall, and with 3ms of contact the average force on the wall by the ball is 392N.

For part C I attempted to use kinematic to solve for t to use in the equation Inet=(F_avg)(delta t)

I substituted a in the first equation with a rewritten version of the V=V0-at to get a=(V-V0)/-t.

So I got:

.4m = 0 + (8.6m/s)t + -1/2(0-8.6m/s)/t

and t=.093 seconds

But then I'm not sure how to find the average force on the player by the ball without the impulse.

Help please!

 

[edgepflow]

What about Newton's 2nd law: F = ma = m (Vf - Vi) / (tf - ti) ?

But, I = F (tf - ti) = m [(Vf - Vi) / (tf - ti)] (tf - ti) = m (Vf - Vi) as you originally stated.