A tennis ball of mass m = 0.060 kg and speed v = 15 m/s strikes a wall at a 45° angle and rebounds with the same speed at 45° (Fig. 7-29). What is the impulse given to the wall?

Question

I know the direction is normal and into the wall, but I cant get the magnitude!

Answer 1

impulse is the change in momentum

the velocity (parallel to the wall) is constant along its flight path

the change in velocity (and momentum) is as you say ... normal to the wall
... the incoming and outgoing speeds are both ... 15 m/s * sin(45º)