- #1
christian0710
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Homework Statement
In a collision, an automobile initially traveling at 50 km/h decelerates at a constant rate of 200 m/s^2. A passenger not wearing a seat belt crashes against the dashboard. Before the collision, the distance between the passenger and the dashboard was 0.60 m. With what speed, relative to the automobile, does the passenger crash into the dashboard? Assume that the passenger has no deceleration before contact with the dashboard.
Homework Equations
+ [/B]The equations for the cars decceleration, velocity and distance traveled are:
a=-a=200m/s^2
v=--a*t +V0
X(t) = -a/2 * t^2 +V0*t 3.The attempt at a solution
we change velocity into m/s
50km/h = 50*1000/60^2 = (125/9 ) m/s
The time at which the car comes to a halt is when velocity = zero
0= a*t –V0
t=V0/a = (125/9)/200 = 5/72sec
The distance the car traveled in that time is
X(5/72) = -200/2 * (125/9)^2 +(125/9)*(5/72) = 0.48 meters
The speed of the passenger must be
0,06m/5/72sec = 8.64m/s
The speed of the car must be
0.48/(5/27) = 6.9m/s
The difference between 8.64 and 6.9 ( I assume is what is meant by relative distance? ) can impossible be 15.6 m/s which is the answer.
Help Is a ppreciated.