# PS Question - Car overtaking truck

Discussion in 'MCAT Study Question Q&A' started by pacer, Sep 6, 2014.

1. ### pacer 2+ Year Member

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A car accelerates at 6 m/s^2 starting from rest. At the same time, a truck travelling at 21 m/s passes the car. How long will it take for the car to overtake the truck?

I am confused about how to set up the formulas for this type of question.

2. ### labqi 5+ Year Member

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I think you do it as follows
Car d=vot + 0.5at2
Truck d=vt

Since they travel the same distance d is equal for both then
vot + 0.5at2 = vt

I am not sure but that's how I would approach. Please correct me if in wrong.

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3. ### justadream 7+ Year Member

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Distance traveled by car = distance traveled by truck

Distance traveled by car = .5 *a * t^2 = .5*6 * t^2 = 3t^2

Distance traveled by truck = 21t

3t^2 = 21t
t = 21/3

It will take 21/3 seconds.

Plug back into either equation to find distance at this point.
Distance = 21t = 21*(21/3) = 147

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