A ball of 2kg strikes a wall with a velocity 1m/s at an angle 30∘ with the horizontal as shown in the figure below. It reflects at the same angle from the wall in 0.1s. Force exerted on the ball will be:
A
20√3N
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B
15√3N
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C
10√3N
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D
5√3N
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Solution
The correct option is A20√3N
Change in momentum of ball perpendicular to the wall =m(vcosθ−(−vcosθ))
(taking rightwards +ve) =2mvcosθ=2×2×1×cos30∘=2×2×√32=2√3kg m/s
We know that force is equal to rate of change of momentum
So, Rate of change of momentum =change in momentumtime=2√30.1=20√3N∴Force on the ball=20√3N