Question

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 ]

Hint:

In vertical wall problems, the applied horizontal force determines the normal reaction, while friction acts vertically to oppose gravity.

Answer 1

Correct Answer: 25

Step 1: For the block to stay stationary, the frictional force $f_s$ must balance the weight $W$.
Step 2: $W = mg = 0.5 \times 10 = 5$ N.
Step 3: Frictional force $f_s = \mu N$, where $N$ is the normal force. Here, $N = F$ (the applied horizontal force).
Step 4: To prevent slipping, $f_{s,max} \geq mg \Rightarrow \mu F \geq mg$.
Step 5: $0.2 \times F \geq 5 \Rightarrow F \geq \frac{5}{0.2} = 25$ N.