Average acceleration of a 50 g super ball bouncing off a wall

[Filenes]

Homework Statement

A 50.0 g Super Ball traveling at 28.0 m/s bounces off a brick wall and rebounds at 19.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the magnitude of the average acceleration of the ball during this time interval? (Note: 1 ms = 10-3 s.)

Homework Equations

i used Vxf = Vxi + at

The Attempt at a Solution

I put vxf = 19, vxi = 28 and t = 3.50 ms and .0035, i get an answer of - 2.57 and -2571 (respectively) and made it positive since its the magnitude, but its wrong. Any ideas?

 

[edziura]

You must account for the fact that the ball changes direction, and so the velocities before and after have different directions.

 

[whyhello112]

F=ma=dp/dt

 

[venkatg]

Impulse = F * t = change in momentum = (mv1 - (- mv2)

F = average force
a = F/m

= (v1 +v2)/t