Free Body Diagrams And Normal Force

As described in NCERT Class 11, Chapter 5 (Laws of Motion), the normal reaction is found by applying the equilibrium condition in the vertical direction, since the block does not move up or down. The forces acting vertically are the weight (50 N down), the vertical component of the applied push (12 N down), and the normal reaction N (up). Setting the net vertical force to zero gives N = weight + downward component = 50 + 12 = 62 N. The downward push increases how hard the floor must support the block, so the normal force rises above the plain weight. Option 50 N ignores the extra downward push entirely. Option 38 N wrongly subtracts the 12 N, which would apply only if the force pulled upward. Option 70 N incorrectly adds the full 20 N applied force instead of only its vertical component. This example highlights that the normal reaction is not a fixed quantity equal to weight, as students often assume, but a responsive force that changes with every other vertical influence on the body. The horizontal component of the applied force, meanwhile, would govern whether the block slides, but it plays no part in the vertical normal-force balance. Plausibility check: a downward-directed applied force must increase the normal reaction above the weight, and 62 N correctly exceeds 50 N by exactly the 12 N vertical component, confirming the result.