Please somebody explain this simple physics problem?

In summary: Learning. I'm glad you find it helpful.In summary, the problem is asking for the time it takes for a car, traveling at a constant speed of 20m/s, to overtake a truck that starts with an acceleration of 2m/second square. After 5 seconds, the truck has traveled 25m and the car has traveled 100m, reaching the starting point of the truck. At the 10th second, the truck has traveled 100m and the car has traveled 200m, reaching the truck. However, at this point, the truck's velocity increases to 22m/s while the car's velocity remains at 20m/s. Therefore, according to the given information,
  • #1
mashac
3
0

Homework Statement



A truck start from a place with an acceleration of 2m/second square.A car passes the same place after 5s with uniform speed of 20m/s. Find the time taken in which car overtakes truck?


Homework Equations





The Attempt at a Solution



Answer given is 10 seconds.

But equation for distance traveled by car is d=vt which means d=20*t and for the truck is d=1/2*a*t^2 which means d=t^2.

By this equation after 5s truck will travel a distance of 25m with a velocity of 10 m/s and car will travel 100m and reach the starting point of the truck. At the 10th second the truck will travel a distance of 100m and car will travel a distance of 200m and reach the truck. At this point the velocity of both truck and car will be 20m/s, but car have no acceleration and the truck accelerates at a rate of 2m/second square. So at the 11th second the truck's velocity will be 22 m/s and car's still will be 20 m/s. So according to my stupid theory the car never over take the truck.

I know I'm somehow wrong about this, but please someone point out that exactly which part of my logic is faulty and kindly explain the logic of right answer which is 10 seconds.
 
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  • #2
But equation for distance traveled by car is d=vt which means d=20*t and for the truck is d=1/2*a*t^2 which means d=t^2.

This isn't right because the car passes the same spot 5 seconds after the truck. So:
d=1/2*a*t^2 for the truck
d=20*(t-5) for the car
 
  • #3
never mind [=> ignore this post]
 
  • #4
Thanks ideasrule, now I understand a little more about the problem.
 
  • #5
An old post for new member !
How Sweet
 

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