I want to calculate the difference in force between a car with a bull bar an a car with crumple zones hitting a pedestrian.(adsbygoogle = window.adsbygoogle || []).push({});

Assume that when the car with bull bar collides with pedestrian, the transfer of velocity is completely transferred

Known variables:

Cars speed: 60kmph ; (16.67 m/s)

Weight of pedestrian: 60kg

Width of pedestrian: 20cm ; (0.2m)

Crumple Zone: crumples 10cm ; (0.1m)

Attempt at Solution

(Bull Bar)

t=d/v

t=0.2/16.67

t=0.012 sec

a=vf-vi /t

a=16.67/0.012

a=1389 m/s

f=ma

f=60*1389

f=83340(N)

This shows that it takes 0.012 seconds for the impact on the pedestrian to be completed, in which time the pedestrian accelerates at 1389 meters per second, which would exert a force of 83340 newtons.

(Crumple Zone)

t=d/v

t=0.2+0.1/16.67

t=0.018 sec

a=vf-vi /t

a=16.67/0.018

a=926 m/s

f=ma

f=60*926

f=55560(N)

This shows that it takes 0.018 seconds for the impact on the pedestrian + the time for the crumple zone to cave, in which time the pedestrian accelerates at 926 meters per second, which would exert a force of 55560 newtons.

Would this be correct for calculating the force exerted on a pedestrian when being hit by a bull bar or crumple zone car?

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# Homework Help: Calculating the difference in force between crumple zone cars and bull bar car

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