Question

With what acceleration (a) should a box descend so that a block of mass M placed in it exerts a force (Mg/4) on the floor of the box? 

(A) (4g / 3) 

(B) (3g / 4) 

(C) g/4 

(D) 3g

Answer 1

Correct option: (B) (3g / 4)

Explanation:

Box is moving down.

F = m(g – a) 

(Mg / 4) = M(g – a) 

hence (g / 4) = g – a 

a = g – (g / 4) 

a = (3g / 4)