3. 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?

Question

3.	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?

anonymous · Answer

Since force is equal to mass times acceleration, multiply 55kg by 20 m/s. Your answer should be 1100 Newtons.

agent0smith · Answer

Use: 
Change in momentum = force multiplied by time. 

or
$$\Large m(v_f - v_i) = F*t$$

alyssakin · Answer

Thank you both!

agent0smith · Answer

btw @alyssakin the answer given by  @rmoultin is not quite correct.

alyssakin · Answer

I was going to try to use the formula and do it myself, so we're all good, thank you for the warning though !!