Question

24 POINTS!!!!!!!!!!!!!!!!!!

Sarah, who has a mass of 55 kg, is riding in a car at 20 m/s. She sees a cat crossing the street and slams on the brakes! Her seatbelt stops her from flying forward, bringing her to rest in 0.5 seconds. How much force did the seatbelt put on Sarah?

Answer 1

change of momentum =mv-mu=m(v-u)=55(0-20)=-1100
rate of change of momentum=-1100/0.5=-2200 this is equal to force applied.
so force=-2200 kg/m^2
negative sign shows force acts in opposite direction to motion.

Answer 2

F = (mass)(acceleration) = ma

m = 55 kg

Vi = 20 m/s

t = 0.5 s

Vf = 0 m/s (since she was put to rest)

a=(Vf-Vi)/t

a=(0-20)/5

a = 40 m/s^2 (decelerating)

F = ma = (55 kg)(40 m/s^2)

F = 2200 N

Hope this answer will be a good help for you.