Question

A ball moving with a momentum of 5 kgm/s strikes against a wall at an angle of 45

Answer 1

Convert the momentum into components as parallel to the wall and perpendicular to the wall.

Initial momentum = 5 kg m/s

perpendicular component = 5 cos 45 = 5/√2 kg m/s

parallel component = 5 sin 45 = 5/√2 kg m/s

After hitting the wall, it reflects at same angle.

So magnitude will the same = 5 kg m/s

parallel component = 5 sin 45 = 5/√2 kg m/s

perpendicular component = -5 cos 45 = -5/√2 kg m/s

(- sign comes due to change in direction)

So you can see that there is no change in parallel component.

Only perpendicular component changes.

So change = 5/√2 kg m/s - (-5/√2 kg m/s)

= 5/√2 kg m/s+5/√2 kg m/s

= 10/√2 kg m/s

=5√2 kg m/s