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A ball falls from a height such that it strikes the floor with velocity 10m/s if the lift ur moving upward with velocity 1m/s then velocity with which the ball rebounds after ellastic collision

yuvaranjini , 6 Years ago
Grade 12th pass
anser 1 Answers
Vikas TU
Dear student 
The soluton to the problem is :
We consider initial velocity of the ball as u1=-10 m/s with reference to ground, We have taken downward direction as negative. The initial velocity of lift is u2=1m/s. After the collision let the velocities be v1 and v2. Since collision is elastic ,the coefficient of restitution e=1. 

Then,  1=(v1-v2)/(u2-u1) or u2-u1=v1-v2. Putting values of u1 and u2 and taking v2=u2 as lift is very heavy, we have ,  v1=2+10=12m/s for observer on ground.
For observer in the lift the lift is stationary and velocity of the ball before and after collision has same value with reversed direction . So, answer for that observer will be 10 m/s
Last Activity: 6 Years ago
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