How long it takes for a car to catch a truck

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Homework Help Overview

The problem involves a car traveling at 91 km/h that is 200 meters behind a truck moving at 81 km/h. Participants are discussing how long it will take for the car to catch up to the truck, focusing on the relative speeds and distances involved.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants are exploring the concept of relative motion and questioning how to apply kinematic equations to the problem. Some express uncertainty about the initial steps and the relevance of the equations provided by the professor.

Discussion Status

There is an ongoing dialogue with some participants attempting to clarify the relationship between the speeds of the car and the truck. A suggestion to convert units for better understanding has been made, but no consensus on the solution has been reached.

Contextual Notes

Participants mention the use of kinematic equations as a constraint, and there is a noted difference between classroom instruction and online homework expectations.

Pioneer98
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Homework Statement


A car traveling 91 km/h is 200m behind a truck traveling 81 km/h . How long will it take the car to reach the truck?

Homework Equations





The Attempt at a Solution

 
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Pioneer98 said:

Homework Statement


A car traveling 91 km/h is 200m behind a truck traveling 81 km/h . How long will it take the car to reach the truck?

Homework Equations



The Attempt at a Solution

Hello Pioneer98. Welcome to PF !

What have you tried?

Where are you stuck?
 
I'm actually not even sure where to start. My professor gave us four kinematic equations to memorize and use. I know how to use those, but the things he went over in class are totally different from the online homework.
 
Motion is always relative. The car is traveling at 10 km/hr faster than the truck. How long will it take to cover 200 m?
 
20 seconds?
 
Pioneer98 said:
20 seconds?
That would be true if car were traveling 10 m/s faster than the truck. Units matter !

Convert 10 km/hr to m/s .
 
10,000 m/hr, 2 7/9 m/s, so it takes 72 seconds for the car to reach the truck. Thanks for the help guys!
 

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