this is what i got, but its based on the assumption that the skier reaches 20ms-1 at the base of the cliff
C)16ms^-2
s=100
u=0
v=20
a=?
t=don't need
rearrange v^2=u^2+2as to get a on its own.
(v^2-u^2)/2s=a
which is (20^2)/25 =16
d)1km
24mph= 32/3 ms^-1
s=?
u=32/3
v= don't need
a=o.2
t=
60
use s=ut+0.5at^2
let s=(32/3)x60 +(0.5x0.2x60^2)= 1000m
which gives you 1000m which is 1 km
probably double check this, I haven't done mechanics since the summer