$($a$)$ A $22\mathrm{.}0-$kg child is riding a

playground merry$-$go$-$round that is rotating at $40\mathrm{.}0$ rev$/$min$.$ What

centripetal force is exerted if he is $1\mathrm{.}35$ m from its center? $($b$)$ What centripetal force is exerted if the

merry$-$go$-$round rotates at $3\mathrm{.}50$ rev$/$min and he is $8\mathrm{.}00$ m from its center?