The correct answer would be B.
Answer:
80m<em>/</em><em>s</em>
Explanation:
Final velocity is given by
v=u+at
when a motorcyclist starts from rest, initial velocity (u) =0
therefore
v=0+4*20
v=80m/s
that's the answer
Since, F = k . ∆x
Therefore, k = F / ∆x = 250 / 0.2 = 1250 N/m
(ps: convert 20 cm into 0.2 m)