Question

A block of mass 2kg is pushed against a rough vertical wall with a force of 40N, coefficient of static friction being 0.5. Another horizontal force of 15N, is applied on the block in a direction parallel to the wall. If the block will move, then its direction would be:

• A. 15${}^o$ with 15N force
• B. 53${}^o$ with 15N force
• C. 45${}^o$ with 15N force
• D. 75${}^o$ with 15N force

Answer 1

The correct option is B 53${}^o$ with 15N force

Downward force is $20N$ and the horizontal force is $15N$.

Thus the total resulatant force is $25N$ and the Normal contact force by the wall is $40N$.

Thus the friction force is $0.5\times 40=20N$.

The block will move, but the direction is $={sin}^{-1}\left(\frac{20}{25}\right)={53}^0$ with the direction of $15N$ force.