- #1
Phykid
- 14
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Homework Statement
Our homework set today was to find out why is it that when you hit someone at 30mph they have a 20% chance of dying. Yet when you hit someone at 40mph they have a 90% chance of dying.
Homework Equations
KE = 1/2 M V^2
The Attempt at a Solution
First of all i found out that 1mile = 1.6km; which means 1 mile = 1600m
I then did 60x60 to find out the amount of seconds in 1 hour: which was 3600 seconds
I then divided 30 by 3600 to get the meters/second; which was 8.333 [reoccuring] m/s
Now I found out the Kinetic Energy. We were allowed to choose which car we used, and I used my fathers. This weighs 2090kg (Mazda 5)
KE = 2090 x (8.333^2) = 145127.278
145127.278 / 2 = 72563.63901 J
This is where the problem came
I then tried it with 40mph
40 / 3600 to get the m/s; which turned out as 0.0111 [reoccuring]
I now thought how the heck could that be right? But I continued & tried to do the equation.
Ke = 2090 x (0.011^2) = 0.25289
0.25289 / 2 = 0.126445
Okay now I'm very confused. Can anyone help me out?
When 30mph KE is 72563.63901 how is 40mph 0.0111?
Thanks,
Phykid