physics help please

Question

A bicycle and its rider have a combined mass of 100. kilograms and a speed of 6.0 meters per second. What is the magnitude of the average force needed to bring the bicycle and its rider to a stop in 4.0 seconds?

Answer 1

Apply conservation of linear impulse and momentum

F_avg * Δt + mV1 = mV2

V1 = 6 m/s

V2 = 0

Δt = 4 seconds

Favg = ?

Solution:

F_avg * Δt + mV1 = mV2

F_avg * 4 + 100*6 = 0

F_avg = -100*6/4 = - 150 N