A 70 kg bicycle rider at rest begin to pump his pedals, resulting in a force of F=5t^2 . What is the rider speed after 8 sec

Q:- A 70 kg bicycle rider at rest begin to pump his pedals, resulting in a force of F=5t^2 . What is the rider speed after 8 sec?

Answer :- 

Given,

            Mass, M = 70 kg

Ar time , t= 8 sec

Force , F = 5(8)^2

            F = 320 Newton 

also , By Newton's second law

Froce , F  =  Ma

           320 = 70a

So, acceleration ,a = 4.571 m/s^2

Also, By equation of motion 

V  = U + at

V = 0 + 4.571x8 

V = 36.568 m/s

So, rider's speed after 8 seconds will be 36.568 m/s