# Thread: Impulse with wall and change of direction

1. ## Impulse with wall and change of direction

Got an impulse question here that I wouldn't normally struggle with, however there's something about a change of direction and not sure what to do here?

A ball of mass 0.1 kg hits a wall at 15 m/s and rebounds at a speed of 5 m/s.

If the path of the ball's diverted by $\frac{\pi}{2}$ radians by the impact, find the magnitude of the impulse exerted on the ball by the wall.

$I = m(v_2 - v_1)$

$I = 0.1(-5 - 15) = -20$, so the magnitude of the impulse would be $20 Ns$?

Think that's right anyway. However I'm not sure how I'd solve it with the change of direction involved?

Thanks in advance

2. If you use vector subtraction, $|m(v_2 - v_1)| = m\sqrt{5^2 + 15^2}$ since the ball bounces at a right angle. This gives the magnitude of the impulse to be $$1.581 N \cdot s.$$ I'm not sure if this is the correct way to do the problem, but it does account for the change in direction.

3. Sorry for the late reply. Thanks that makes sense, not used to dealing with vector velocities in questions like these. Thanks again!