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Most Important Selected Qs for JEE AdvancedPhysicsRotational Motion

There is a rectangular plate of mass M kg of dimensions ( a b ) . The plate is held in horizontal position by striking n small balls each of mass m per unit areaper unit time. These are striking in the shaded half region of the plate. The balls are colliding elastically with velocity v . What is v ? It is given n =100, M =3 ~kg , m =0.01 ~kg ; b =2 ~m ; a =1 ~m ; g =10 ~m / s ^2

Correct answer

10

Step-by-step solution

Taking torque about axis OO ^ & putting it equal to zero aligned & ( _ net )₀=0 & mg b 2 - F 3 ~b 4 =0 aligned F = 2 mg 3 (i) F = n (2 mv ) ( ab 2 ) (ii) From (i) & (ii), putting the values we get v =10 ~m / s

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