NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice
A block of mass m = 2 kg is placed on a plank of mass M = 10 kg , which is placed on a smooth horizontal plane, as shown in the figure. The coefficient of friction between the block and the plank is μ = 1 3 . If a horizontal force F is applied on the plank, then the maximum value of F for which the block and the plank move together is g = 10 m / s 2
Options
- A50 N
- B40 N
- C120   N
- D100   N
Correct answer
B. 40 N
Step-by-step solution
a = F M + m assuming no slipping between   m and M This means friction between the block and plank is f = m a = m F m + M f = m F m + M ≤ μ m g ⇒ F ≤ M + m g 3 ⇒ F ≤ 40   N