$($b$)$ The $0\mathrm{.}5$ kg collar is pulled down the curved rod by the spring whose stiffness

is $20\frac{N}{m}$ and whose free $($unstretched$)$ length is $500$ mm $.$ Neglect friction. If

the collar has a speed of $10\frac{m}{s}$ in the position shown, determine the

corresponding acceleration of the collar and the force the collar exerts on the

rod. $(1)$

$(10)$