Question

A block of mass $15kg$ is placed on a long trolley. The coefficient of friction between the block and trolley is $0.18$. The trolley accelerates from rest with $0.5{m/s}^2$ for $20$ sec, then what is the friction force?

• A. $3.5N$
• B. $133.3N$
• C. $7.5N$
• D. $Noneofthese$

Answer 1

The correct option is C $7.5N$

• The psuedo force on the block is mass of block multiplied by acceleration of trolley so it comes to $15\times 0.5$ i.e., 7.5 Newton now the friction has a maximum value of $\mu mg$ put $\mu =0.18$ and $g=9.8$ we get maximum value of friction as 26.46 Newton so it able to oppose the psuedo force so the value of frcition will not be maximum it will be just equal to psuedo force to help it move with trolley and to avoid to slip.
• So answer is $7.5N$ Option C