Change in momentum after hitting a wall

[gake]

Homework Statement

32) The change in momentum, in kg m/s, that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall
and bounces back at 2.0 m/s is
A) 2.
B) 4.
C) 6.
D) 8.
Answer: C

Homework Equations

Momentum==Mass*Velocity

The Attempt at a Solution

I get A.

Momentum₁==1*4
Momentum₂==1*2

Momentum₁-Momentum₂==2

 

[lewando]

Consider the "sign" associated with the two velocities.

 

[gake]

What a dumb mistake! Thanks :)