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The coefficient of static friction between a wooden block of mass 0.5 kg and a vertical rough wall is 0.2. The magnitude of horizontal force that should be applied on the block to keep it adhere to the wall will be ______ N. [g = 10 ms⁻²]

1. 1
2. 2
3. 5
4. 25

Correct answer: 25

Solution

To keep the block adhered to the wall, the applied horizontal force must counteract the force of gravity acting on the block. The weight of the block is 0.5 kg multiplied by the acceleration due to gravity (10 m/s²), which equals 5 N. The maximum static friction force is the coefficient of static friction (0.2) multiplied by the normal force (the applied horizontal force). Setting the maximum friction equal to the weight gives the equation: 0.2 * F = 5 N, leading to F = 25 N.

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