Answer:
F = -319.2 N
Step-by-step explanation:
Given that,
The mass of a bicyclist, m = 70 kg
Mass of the bicycle = 9.8 kg
The speed of a bicycle, v = 16 m/s
We need to find the magnitude of the braking force of the bicycle come to rest in 4.0 m.
The braking force is given by :

So, the required force is 319.2 N.