At the instant traffic lights turn green, a car starts with a constant acceleration fo 2m/s^2. At the same instant, a truck traveling with a constant speed of 10m/s overtakes and passes the car. How far beyond the starting point will the car overtake the truck? How fast will the car be travelling at that instant? a)100m,20m/s b)100m,10m/s c)150m,20m/s d)150m,10m/s c)

Asked by Shikha Vanjani | 26th Jul, 2013, 04:50: PM

Expert Answer:

Let the car and truck meet after t sec and the distance travelled would be equal to s m. 
For the car, s = (at^2)/2 = t^2

For the truck, s = 10t
When the distances are equal 10t = t^2

t^2 - 10t = 0
t(t-10) = 0
t = 0 or t = 10 sec.
Since at t = 0, the car and truck are at the light itself, so, they meet up at  t= 10 sec. 

s = 10*10 = 100 meters from the light.
Speed of the car = at = 2*10 = 20 m/s
Hence, option a is correct. 

Answered by  | 27th Jul, 2013, 09:26: AM

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