Answer
(a) $3.0N$
(b) No
Work Step by Step
(a) We can find the required force of friction as follows:
$f_s=-Kx$
We plug in the known values to obtain:
$f_s=-(150)(-0.02)$
$f_s=3.0N$
(b) We know that $f_s=-Kx$, this equation shows that force of friction does not depend on mass. Thus if the mass doubled, even then the answer to part (a) will not change.
