<PRE><B>Question 264770</B>
At the instant the traffic light turns green, an automobile that has been waiting at an intersection starts ahead with a constant acceleration of 2.80 m/s^2. At the same instant, a truck, traveling with a constant speed of 14.7 m/s, overtakes and passes the automobile.
How far beyond its starting point does the automobile overtake the truck?
How fast is the automobile traveling when it overtakes the truck?
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For the car, s = (at^2)/2 = 3.92t^2
For the truck, s = 14.7t
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When the distances are equal 14.7t = 3.92t^2
3.92t^t - 14.7t = 0
t = 0 (at the light)
t = 14.7/3.92 = 3.75 seconds
At 3.75 seconds, the auto catches up to the truck.
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s = 14.7*3.75 = 55.125 meters from the light.
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Auto speed = 3.92*3.75 = 14.7 m/sec when it overtakes the truck
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