Consider an old car from the 60\'s that was built a little more rigid. You could
ID: 1469448 • Letter: C
Question
Consider an old car from the 60's that was built a little
more rigid. You could fall asleep behind the wheel, crash into a tree, wake up and be like what!?
Then put it in reverse and drive home assuming you are not too badly shaken up! A new car would
be totaled if you hit a tree like that with any significant speed. So why?! Let's assume we have two
cars that have the same mass (2000kg). These cars are driving straight at a tree with a speed of 30
m/s (67 mph). The first car is built rigid as to not destroy the car during impact and after the
collision has some bumper damage but the damage is only as thick as the bumper. Let's call it about
15cm. The second car is build less rigid and crumples most of the length of the front of the car.
This car crumples a length of approximately 60cm. Using work/KE, what is the force exerted on
each car (and thus directly influencing your day!) if we assume the force is constant? Discuss the
results in terms of car construction.
Explanation / Answer
Here ,
mass of car , m = 2000 Kg
initial speed , u = 30 m/s
for the rigid car ,
d = 0.15 m
Using work energy theorum
0.5 * 2000 * 30^2 = F * 0.15
F = 6 *10^6 N
the force acting is 6 *10^6 N
--------------------
for d = 60 cm = 0.60 m
Using work energy theorum
0.5 * 2000 * 30^2 = F * 0.6
F = 1.5 *10^6 N
the force acting is 1.5 *10^6 N