Magnitude of change in linear momentum

[studypersist]

Homework Statement

A 0.70 kg ball is moving horizontally with speed of 9.6 m/s when it strikes a vertical wall. The ball rebounds with speed of 1.3 m/s. What is the magnitude of the change in linear momentum of the ball?

Homework Equations

Dp = mv(f) - mv(i)

The Attempt at a Solution

I solved for mv(f) and mv(i). Solved for Dp which I got -5.81 which is wrong.

 

[Doc Al]

Hint: The initial and final velocities point in opposite directions.

 

[studypersist]

-.91 - 6.72 = -7.63

Is the answer positive because magnitude is positive?

 

[Doc Al]

That is correct.