1thanks
this q was in one of the tests on the site
A ball hits a plank lying on the ground (ball's velocity at the time of hitting the plank is 10i+10j). The coefficient of friction is between the ball and the plank is 0.5. There is no friction between the plank and the ground. The coefficient of restitution is 1. Find the velocity of the plank after the ball leaves. Mass of the plank is 10 times the mass of the ball.
a) 1m/s
b) 0.5m/s
c) 0.25m/s
d) none of these
Explaination :
The normal impulse that acted on the ball during the collision is 20m kgm/s. (M is the mass of the ball)
So the frictional impulse would be mu x Normal impulse.
So that will be 10m kgm/s
So the change in momentum of the plank will be 10m/10m m/s = 1m/s
plz explain the line
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UP 0 DOWN 0 0 2
2 Answers
62F≤μN
When you have an impulse it will be the integal
so ∫F.dt ≤ ∫ μN dt
so ∫F.dt ≤ μ ∫ N dt
where normal impulse is ∫ N dt
while frictional impulse is ∫F.dt
Hence the above statement..
thought the question should have specifically mentioned limiting friction is acting all the time..