Question

On the horizontal surface of a truck a block of mass 1 kg is placed $(\mu = 0.6)$ and truck is moving with acceleration $5 m/sec^2$ then the frictional force on the block will be

• A. 5 N
• B. 6 N
• C. 5.88 N
• D. 8 N

Answer 1

Answer: (A)

5 N

Answer 2

$f_{rl}=\mu_sN=\mu_s\times mg=0.6\times1\times10=6 N.$ where $f_{rl}$ is the force of limiting friction. Pseudo force $=ma = 1\times 5 ; F = 5\, N$ If $F < f_{rl}$, block does not move. So static friction is present. Static friction = applied force . $\therefore f_r=5\, N$.