Question

A force of $51N$ is exerted on a block of mass $10Kg$, as shown in the figure. Find the acceleration of the block if it is initially at rest.
${\mu }_s=0.5$
${\mu }_k=0.3$

Answer 1

$0\le f_s\le {\mu }_{s}N$
$0\le f_s\le 50$
Now 51 > 50
$\therefore$ Block will move but if the block starts moving then kinetic friction is involved.
$K_F={\mu }_{k}N=0.3\times 100=30N$
$\therefore 51-30=10a$
$\therefore a=2.1m/s^2$