Q. 134.3( 139 Votes )

# A hockey ball of mass 200 g travelling at 10 ms^{-1} is struck by a hockey stick so as to return it along its original path with a velocity of 5 ms^{-1}. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.

Answer :

Firstly, we will calculate the initial momentum:

Given,

Mass of hockey ball, m_{1}= 200 g

(We know that 1kg=1000gram)

= kg

= 0.2 kgInitial velocity, v_{1} = 10 m/s (Given)

So,

Initial momentum = m

_{1}

*×*v

_{1}= 0.2 × 10

= 2 kg m/s (i)

Now, we will calculate the final momentum:

Given,

Mass of hockey ball, m_{2} = 200 g

(We know that 1kg=1000gram)

Final velocity, v_{2}*=* - 5 m/s (As the ball is going in reverse direction)

Final momentum = m_{2} × v_{2}

= - 1 kg m/s (ii)

Now,

Change in momentum = Final momentum – Initial momentum= -1 -2

= (- 3) kg m/sTherefore, the change in momentum of the hockey ball is **3 kg m/s.**

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