Question

A plank is held at an angle a to the horizontal on two fixed supports A and B. The plank can
slide against the supports (without friction) because of the weight Mg sin a. Acceleration and
direction in which a man of mass 'm' should move so that the plank does not move are
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Answer 1

the force acting of the plank in downward direction

F = Mg sin x

there are two forces acting on the man in downward direction they are f and mg sin x

According to Newton's second law of motion ,

mg sin x + f = ma

mg sin x + Mg sin x = ma

g sin x ( m+ M ) = ma

g sin x ( m+M /m ) = a

g sin x (1+ M / m) = a

a = g sin x (1+ M / m) will act down the inclined plane