Question

A body of mass $60kg$ is dragged with just enough force to start moving on a rough surface with coefficients of static and kinetic friction $0.5$ and $0.4$ respectively. On applying the same force what is the acceleration?

• A. $0.98m/s^2$
• B. $9.8m/s^2$
• C. $0.54m/s^2$
• D. $5.292m/s^2$

Answer 1

The correct option is A $0.98m/s^2$

See the maximum static friction that can act on the body is Umg = $0.5\times 60\times 9.8=294N$
now since the force is just above 300 N, the body will translate and the type of friction now will be kinetic instead of static.
Hence the net acceleration is
$294-0.4\times 60\times 9.8/60=0.98m/s^2$