Question

An iron block of mass $5\, kg$ is kept on a trolley. If the trolley is being pushed with an acceleration of $5\,m / s$ $2$, what will be the force of friction between the block and the trolley surface? (Take the coefficient of static friction between the block and the trolley surface to be $0,8$).

• A. Zero
• B. 5 N
• C. 4 N
• D. 25 N

Answer 1

Answer: (D)

25 N

Answer 2

Applied force $=m \times a=5 \times 5=25$ Limiting friction $=\mu\, m g=0.8 \times 5 \times 10=40$ For the given condition applied force is very smaller than limiting friction $\therefore$ Static friction on a body $=$ applied force $=m a$ $=5 \times 5=25 \,N$