The spring constant $k$ is $3\frac{N}{m}$ and its free$-$length is $1$ m $.$ Remember spring

force is equal to the spring constant times the stretch in the spring. The $3$ N

collar has a coefficient of kinetic friction of $0\mathrm{.}1.$ The collar is at rest at A when

it is dropped. The collar is moving downward as it passes point $C$ where $y=$

$1\mathrm{.}5$ m $.$ The weight of the blue rod is $4$ N $.$

a$)$ What is the acceleration of the collar the moment it is passing $C?$

Answer $=$