JEE Main202120 Jul 2021Morning ShiftPhysicsLaws of MotionActual
A steel block of 10 kg rests on a horizontal floor as shown. When three iron cylinders are placed on it as shown, the block and cylinders go down with an acceleration 0 . 2 m s - 2 . The normal reaction R ' by the floor if mass of the iron cylinders are equal and of 20 kg each is in N , [Take g = 10 m s - 2 and μ s = 0 . 2
Options
- A716
- B686
- C714
- D684
Correct answer
B. 686
Step-by-step solution
Writing force equation in vertical direction, M g - N = M a ⇒ 70   g - N = 70 × 0 . 2 ⇒ N = 70 [   g - 0 . 2 ] = 70 × 9 . 8 ∴ N = 686 newton Note: Since there is no compressive normal from the sides, hence friction will not act. Hence option 2 .