Friction

From NCERT Class 11, Chapter 5 (Laws of Motion), the limiting (maximum) static friction is given by f_max = μ_s N, where N is the normal reaction. On a horizontal floor with only weight acting vertically, the normal reaction equals the weight, so N = 60 N. The block is on the verge of sliding when the applied horizontal force equals the limiting static friction, so f_max = 24 N. Rearranging, μ_s = f_max / N = 24 / 60 = 0.4. Option 0.6 incorrectly inverts the ratio as 60/24 scaled, or confuses force with weight. Option 0.25 corresponds to taking 24/96, using a wrong normal force. Option 0.5 corresponds to 30/60 and does not match the given applied force. Plausibility check: coefficients of static friction for wood on a typical floor lie around 0.3 to 0.5, so 0.4 is physically realistic, and being dimensionless it correctly carries no units, confirming the result.