A trajectile, of mass 20 g, traveling at 350 m/s, strikes a steel plate at an angle of 30-degrees with a plane of the plate. It ricochets off at the same angle, at a speed of 320 m/s. What is the magnitude of the impulse that the steel plate gives to the trajectile?

Answer 1

Find the velocity components perpendicular to the plate, and parallel to the plate.

initial: perpendicular speed=350sin30
parallel speed=350cos30

final: perpendicular:320sin30
parallel: 320 sin30

find the change of momentum for each direction.

perpendicularspeed change: sin30(350+320)=670sin30
parallel speed change: cos30(350-320)
30cos30

and momentum changes in those directions are that speed change multiplied by mass.

resultant velocity change:

velocitychange=sqrt(perpend^2 + parall^2)
= sqrt ((30cos30)^2 + (670sin30)^2)
calculate that out, multiply it by mass m.

That is the change of momentum, and it is the same as impluls.