Physics Problem! (about the force of a ball hitting a wall)?

M

Meee

New member
A ball is traveling with a speed of 3.0 m/s. It collides with a vertical wall and rebounds with a horizontal speed of 2.0m/s.

The mass of a ball is 1.0kg and it is in contact with the wall for 0.20 seconds. The magnitude of the force that the ball exerts on the wall is:

a) 0.20N
b) 0.25N
c) 20N
d) 25N

I'm trying to study for a test, and i cannot get any of these answers!

Here is what i did:
Average acceleration = change in velocity / change in time
Average acceleration = 3.0m/s - 2m/s / 0.20s
Average acceleration = 5m/s^2 (seconds squared)

then:
Force= mass * acceleration
Force= 1.0kg * 5m/s^2
Force = 5N

But that isn't one of the answers!

Can someone tell me where i'm going wrong? :)
Hodgepodge! Thank you so much! you have no idea i have been fighting with that question! and over a stupid negetive sign... *sigh* well thanks!
 
For ur change in velocity its 5 m/s not 1m/s, because when the ball is going towards the wall the velocity is 3m/s but when it rebounds it is (-2m/s)
3- -2mls = 5m/s
so then u divide by 0.20s
and u get 25m/s^2
so ur answer is d)25N
 
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