A $59,4$ kg pole$-$vaulter falls from rest from a height of $4\mathrm{.}5$ m onto a foam$-$rubber pad. The pole$-$vaulter comes to rest $0\mathrm{.}28$ s arter davity on the as$($a$)$ Calculate the athlete's velocity just before reaching the pad.$-16\mathrm{.}07$m$/$s downward$($b$)$ Calculate the constant force exerted on the pole$-$vaulter due to the collaion.