- #1
HSkiddave
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Homework Statement
Pete got into into a car accident and collided with another vehicle, which resulted in the death of the second vehicles passenger, David. Whether Pete was speeding or not determines if he goes to jail. The speed limit where he got into the accident was 45mph. How fast was pete going at the point of collision and will he go to jail?
Given Data :
Mass of David’s Car(m2)
1115lbs
Mass of Pete’s car (m1)
1755lbs
Distance the cars skidded
13m
Final velocity post skid
0mph
Time of skid
22sec
Initial velocity of David’s car
47mph
Speed limit
45mph
Homework Equations
$$ (m1v1) + (m2v2) = (m1 + m2)Vf $$
The Attempt at a Solution
First I converted from lbs and mph to kg and m/s for the masses and velocity since we use kg and m/s in my class, I don't know if this was neccesary.
1151 lbs = 505.8 kg
1755 lbs = 796.1 kg
47mph = 21.01 m/s
Then I used my equation
$$ (m1v1) + (m2v2) = (m1 + m2)Vf $$
$$ (796.1*v1) + (505.8*21.01) = (796.1 + 505.8)0 $$
$$ (796.1*v1) + (10626.858) = 0 $$
$$ 796.1*v1/796 = -10626.8/796 $$
$$ v1 = 13.35 m/s $$
I then converted that from m/s to mph and got 29.86mph, which would mean he would not be speeding and not go to jail.
Although I got all the way through, i feel I am wrong since they gave me the data for time and distance and i never even used them, which makes me feel like I am forgetting something. Could someone help me out or check it to see if i did skip a step?