(a) Calculate the force needed to bring a 1050 kg car to rest from a speed of 90

Question

(a) Calculate the force needed to bring a 1050 kg car to rest from a speed of 90.0 km/h in a distance of 115 m (a fairly typical distance for a nonpanic stop).

(b) Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2.00 m. Calculate the force exerted on the car and compare it with the force found in part (a), i.e. find the ratio of the force in part(b) to the force in part(a).
(force in part (b) / force in part (a))

CANT FIGURE OUT PART B PLEASE HELP!

I FIGURED OUT PART A SO THATS RIGHT, I JUST DONT KNOW HOW TO FIND B

(a) Calculate the force needed to bring a 1050 kg car to rest from a speed of 90.0 km/h in a distance of 115 m (a fairly typical distance for a nonpanic stop). -2853.26 N (b) Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2.00 m. Calculate the force exerted on the car and compare it with the force found in part (a), i.e. find the ratio of the force in part(b) to the force in part(a) (b)S (force in part (b) / force in part (a))

Explanation / Answer

part a force applied in negative x direction

fy energy conservation

F*d=.5mv2

F*115=1050*(90*5/18m/s)2

F=2853.2608 in negetive x direction

part b

momentum equation

F.dt=initial momentumfinal momentum

F*(2*60s) =1050*90-0

F=218.75N

force in part (a)/ force in part (b)=218.75/2853.26=0.0766666

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