Torque balance for tipping

Steps:

• Center of mass is at horizontal midpoint: 4 cm (0.04 m) from pivot P.
• Torque from weight about P: 50 N × 0.04 m = 2 Nm (resisting rotation).
• Horizontal force F applied at top of block: lever arm is height of 40 cm (0.4 m).
• Minimum F to start rotation: F × 0.4 m = 2 Nm, so F = 5 N.

Why B is correct:

• Matches torque equilibrium formula τ = F × d, where F balances weight's torque at the top edge.

Why the others are wrong:

• A: Underestimates by halving the required torque balance.
• C: Overestimates by using full base width (8 cm) as lever arm for weight.
• D: Overestimates by ignoring height and misapplying force ratios.

Final answer: B