Just before striking the wall, a racquet ball with mass m = 0.244 kg is moving t

Question

Just before striking the wall, a racquet ball with mass m = 0.244 kg is moving toward the wall at v = 14.8 m/s and at an angle of ? = 27° with respect to the horizontal. The ball makes a perfectly elastic collision with the solid, frictionless wall and rebounds at the same angle with respect to the horizontal. The ball is in contact with the wall for t = 0.067 s (assume the ball grips the wall during the collision so gravity does not act on it).

1) What is the magnitude of the initial momentum of the racquet ball?

2) What is the magnitude of the change in momentum of the racquet ball?

3) What is the magnitude of the average force the wall exerts on the racquet ball?

Explanation / Answer

A) initial momentum of the ball is m1*u1 = 0.244*14.8 =3.6112 kg*m/s

B) along normal to the wall

initial velocity component is u1*cos(theta) = 14.8*cos(27) = 13.18 m/s

final velocity component is -u2*cos(theta) = -14.8*cos(27) = -13.18 kg*m/s

along the wall both the initial velocity and final componet velocity are in same direction ,he3nce there is no chnage in momentum along the length of the wall

change in momentum is 2*13.18 = 26.37 kg*m/s

3) Favg*dt = 26.37

Favg = 26.37/0.067 = 393.6 N

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