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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: joey7 on October 29, 2013, 06:19:30 pm

Title: Collisions
Post by: joey7 on October 29, 2013, 06:19:30 pm: Came across this question in a Trial Exam

There are two collisions:

In collision 1: Car A of mass 1100 kg travelling at 20ms^-1 collides head on with another identical car travelling at 20ms^-1 in the opp. direction
In collision 2: Car A of mass 1100 kg travelling at 40ms^-1 crashes into a solid wall
In both collisions Car A comes to rest in 0.2 seconds

Which collision would cause car A to suffer more damage?

Answer confused me abit appreciate if someone could explain it
Title: Re: Collisions
Post by: Stevensmay on October 29, 2013, 06:31:11 pm: I did this question using impulse. $\Sigma F = \frac{m \Delta v}{\Delta t}$

Collision 1.
$\Sigma F = \frac{1100 *20}{.2}=100000N$

Collision 1.
$\Sigma F = \frac{1100 *40}{.2}=220000N$

Which suggests that collision two will be worse.

Better way to do it

Collision one.
$E_k=\frac{1}{2}mv^2$
$E_k=\frac{1}{2}1100*20^2 + \frac{1}{2}1100 * 20^2$
$E_k=220000J$

Collision two.
$E_k=\frac{1}{2}mv^2 + 0$
$E_k=\frac{1}{2}1100 *40^2$
$E_k=880000J$

So again collision two will be worse.
Title: Re: Collisions
Post by: Alwin on October 29, 2013, 06:32:49 pm: Quote from: SocialRhubarb on October 29, 2013, 06:26:41 pm
I would've thought the amount of 'damage' would be identical in both collisions, assuming that damage is related to the amount of force acting on the car.

er no, sorry socialrhubarb. for the first collision, the force acts on BOTH cars so then they each experience a collision at 20ms^-1 with a solid inanimate surface (wall)

now since I ain't no nliu with all the technical jargo, I found a nice video for you :D

http://dsc.discovery.com/tv-shows/mythbusters/videos/mythssion-control.htm