Answer:
42.5N
Step-by-step explanation:
According to the Newton's second law of motion:
The net force is equated to the product of the mass times the acceleration.
Force(F)=mass(m)*acceleration(a)
first we have to find the acceleration of the bicycle
![accceleration=(Velocity .difference)/(time) \\a=((4-0)ms^(-1) )/(8s) \\a=0.5ms^(-2)](https://img.qammunity.org/2020/formulas/physics/middle-school/ks4ish9ny139cikw8fyd85dgsykxhywx60.png)
![F=85kg*0.5ms^(-2)\\ =42.5N](https://img.qammunity.org/2020/formulas/physics/middle-school/aw39rjr9a73qbfe6s4qq0n0vf14qa5hnng.png)