Question

a hockey ball of mass 200g travelling from West to east at 10m/s is struck by a hockey stick were in contact for 0.2s .calculate the initial velocity and the final momentum of the ball and the rate of change of momentum of the ball.

Answer 1

Answer:

Initial velocity=0 m/s

Final momentum of ball = 2 Kg m/s

Rate change in momentum = 10 N

Explanation:

Consider ball and hockey stick as a system.

According to conservation of momentum,

momentum of system before collision = momentum of system after collision

The momentum of system before collision = $m_bv_b+m_sv_s$

where subscript 's' stands for stick and 'b' stands for ball. 'v' is the velocity and 'm' is the mass.

$=0+m_sv_s$ ( because initially ball is at rest before hitted by stick)

The initial velocity of the ball is 0

After hitting the ball stick comes to rest and ball gains a velocity.

So, the final momentum of the ball is $m_bv_b$

$p_f=m_bv_b=(0.2)(10)=2Kgm/s$

The final momentum of ball is 2Kgm/s

Change in momentum of the ball = final momentum of the ball- initial momentum of the ball

$=2-0=2Kgm/s$

So, the rate change in momentum of the ball $=2/0.2=10N$