Question

A man of mass m moves with a constant speed on a plank of mass M and length L kept initially at rest on a frictionless horizontal surface from one end to other end in time T. The speed of plank relative to ground while the man is moving is ?

Answer 1

Let the distance moved by the plank be x.

So the distance that the man will move is L - x.

Applying Conservation of Linear Momentum,

Mx = m(L - x)
Mx = mL - mx
Mx + mx = mL
x(M + m) = mL
x = mL / (M + m)

Distance moved by the plank in T seconds is mL/( M + m).

Speed = Distance ÷ Time
Speed = mL/ [ (M + m)T]

Hope This Helps You!

Answer 2

Here your answer 1.anything deminator is total mass only