Question

Three blocks `A` , `B` and `C` of masses `4kg` , `2kg` and `1kg` respectively are in contact on a frictionless surface, as shown. If a force of `14N is applied on the `4kg` block, then the contact force between `A` and `B` is.

A. `6mg`
B. zero
C. `2mg`
D. `3mg`

Answer 1

Correct Answer - b
As block of mass `2m` moves upwards with a constant velocity its acceleration `a =0`
Net force on the block `F =ma = Zero` .