I\'m having trouble setting up the equations for this problem.Please help. Seatb

Question

I'm having trouble setting up the equations for this problem.Please help.


Seatbelts provide two main advantages in a car accident: (i) theykeep you from being thrown from the car, and (ii) they reduce theforce that acts on you during the collision to survivable levels.The second benefit can be illustrated by comparing the net forceexerted on the driver of a car in a head-on collision with andwithout a seatbelt.
(a) A driver wearing a seatbelt decelerates at the same rate as thecar itself. Since modern cars have a "crumple zone" built into thefront of the car, the car will decelerate over a distance ofroughly 1.0 m. Find the net force acting on a 54 kgdriver who is decelerated from 18 m/sto rest in a distance of 1.0 m in kN.



(b) A driver who does not wear a seatbelt continues to move forwardwith a speed of 18 m/s(due to inertia) until something solid is encountered. The drivernow comes to rest in a much shorter distance -- perhaps only acentimeter. Find the net force acting on a 54kgdriver who is decelerated from 18 m/sto rest in 1.0 cm in kN.
I'm having trouble setting up the equations for this problem.Please help.

Seatbelts provide two main advantages in a car accident: (i) theykeep you from being thrown from the car, and (ii) they reduce theforce that acts on you during the collision to survivable levels.The second benefit can be illustrated by comparing the net forceexerted on the driver of a car in a head-on collision with andwithout a seatbelt. (a) A driver wearing a seatbelt decelerates at the same rate as thecar itself. Since modern cars have a "crumple zone" built into thefront of the car, the car will decelerate over a distance ofroughly 1.0 m. Find the net force acting on a 54 kgdriver who is decelerated from 18 m/sto rest in a distance of 1.0 m in kN.



(b) A driver who does not wear a seatbelt continues to move forwardwith a speed of 18 m/s(due to inertia) until something solid is encountered. The drivernow comes to rest in a much shorter distance -- perhaps only acentimeter. Find the net force acting on a 54kgdriver who is decelerated from 18 m/sto rest in 1.0 cm in kN.

Explanation / Answer

Part a x = 1/2(vo + v)t 1m = 1/2(18 + 0)t 2/18 = 0.11s Ft = mv F = mv/t = 54kg*18m/s/0.111s = 8756.76N = 8.76kN Part b x = 1/2(vo + v)t .01m = 1/2(18 + 0)t .02/18 = 0.0011s Ft = mv F = mv/t = 54kg*18m/s/0.00111s = 875676N = 875.7kN Hope that helps x = 1/2(vo + v)t .01m = 1/2(18 + 0)t .02/18 = 0.0011s Ft = mv Ft = mv F = mv/t = 54kg*18m/s/0.00111s = 875676N = 875.7kN Hope that helps

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