A hockey ball, of mass 200 g, travelling from west to east, at 10 m/s is stuck by a hockey stick. As a result the ball gets turned back and now has a speed of 5 m/s. The ball and hockey stick were in contact for0.2 s.
(i) Calculate the initial and final momentum of the ball.
(ii) Calculate the rate of change of momentum of the ball.
(iii) What are the SI units of (a) momentum and (b) rate of change of momentum?
(iv) Calculate force exerted by the hockey stick on the ball.
Answers
Answer:
A hockey ball, of mass 200 g, travelling from west to east, at 10 m/s is stuck by a hockey stick. As a result the ball gets turned back and now has a speed of 5 m/s. The ball and hockey stick were in contact for0.2 s.
(i) Calculate the initial and final momentum of the ball.
(ii) Calculate the rate of change of momentum of the ball.
(iii) What are the SI units of (a) momentum and (b) rate of change of momentum?
(iv) Calculate force exerted by the hockey stick on the ball.
Answer:
GIVEN:-
Mass of ball (m) = 200 g = 0.2 kg
Initial velocity of ball ({u_1}u
1
) = 10 m {s^{-1}}s
−1
Initial momentum of ball = {mu_1}mu
1
= 0.2 kg x 10 m{s^{-1}}s
−1
= 2 N s
Final velocity of ball {(u_2)}(u
2
) = - 5 m {s^{-1}}s
−1
(Minus sign denotes that ball is moving in opposite direction.)
Final momentum of ball ={mu_2}mu
2
= 0.2 kg x -5 m{s^{-1}}s
−1
= -1 N s
Change in momentum = Final momentum - Initial momentum = - 1Ns - 2Ns = - 3N s. (Minus sign denotes change in momentum in the direction opposite to the direction of initial momentum of the ball.
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