Calculating Impulse in a Collision

[itsmarasilly]

Homework Statement

Before a collision, a 26 kg object is moving at +10 m/s. Find the impulse that acted on the object if, after the collision, it moved at the following velocities.

a) +8.0 m/s
b) -8.0 m/s

Homework Equations

Impulse = change in momentum
= mass * change in velocity
= m * (vf - vi)

The Attempt at a Solution

a) = 26 (+10 m/s - +8.0 m/s), impulse = 52?
b) = 26 (+10 m/s - -8.0 m/s), impulse = 468?

 

[alphysicist]

Hi itsmarasilly,

Homework Equations

Impulse = change in momentum
= mass * change in velocity
= m * (vf - vi)

The Attempt at a Solution

a) = 26 (+10 m/s - +8.0 m/s), impulse = 52?
b) = 26 (+10 m/s - -8.0 m/s), impulse = 468?

If you compare these to the last equation in your "Relevant equations" section, it looks like you have the initial and final velocities switched.

 

[itsmarasilly]

oh okay, got it. thanks! :)