Please somebody explain this simple physics problem?

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Homework Help Overview

The problem involves a truck accelerating from rest and a car traveling at a constant speed. The truck has an acceleration of 2 m/s², while the car passes the starting point 5 seconds later at a speed of 20 m/s. The question seeks to determine the time it takes for the car to overtake the truck.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to analyze the distances traveled by both the truck and the car using equations of motion. Some participants question the initial setup of the equations, particularly the timing of the car's travel relative to the truck's acceleration.

Discussion Status

Participants are exploring different interpretations of the problem setup, particularly regarding the timing of the car's travel and the equations used to represent the distances. Some guidance has been offered to clarify the equations for distance based on the timing of the car's passage.

Contextual Notes

There is a noted confusion regarding the timing of the car's travel, as it passes the starting point 5 seconds after the truck begins its motion. This aspect is under discussion and may influence the understanding of the problem.

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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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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
 
never mind [=> ignore this post]
 
Thanks ideasrule, now I understand a little more about the problem.
 
An old post for new member !
How Sweet
 

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