Frames of reference and vectors problem

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Homework Help Overview

The problem involves a car moving north at 35 km/h and a truck moving west at 42 km/h. The question seeks to determine the speed and direction of the truck as perceived by the car's driver, specifically addressing a discrepancy in the direction of the resultant vector.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the resultant speed using the Pythagorean theorem and question the direction of the vector. Some seek clarification on the terminology used, particularly regarding the term "caravan."

Discussion Status

The discussion is ongoing, with participants providing different interpretations of the direction of the resultant vector. Some have suggested graphical or numerical methods to resolve the direction issue, while others are clarifying the terminology used in the problem statement.

Contextual Notes

There is a potential ambiguity regarding the term "caravan," which may refer to different concepts in British and American English. Additionally, the original poster expresses confusion about the direction of the resultant vector compared to the book's solution.

notsoclever
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Homework Statement


A car is moving toward north with a speed of 35 km/h. A truck travels toward west with a speed of 42 km/h.
Which is the speed of the caravan according to the car's driver?

Homework Equations

The Attempt at a Solution


The solution given by the book is 15 m/s with direction south-west, but I get the solution of 15 m/s with direction north-west and I cannot get the reason.
Can you help me with this?
Thanks
 
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Please show or describe your calculation/drawing, which gave you the results (15 m/s, NW).
 
I used Pitagora theorem to get the value of 54 km/h that is 15 m/s, but the direction of the vector is north-west and not south-west.
 
You've already got the velocity correct in the first place, the direction is correct like the book says (SW). Did you try to solve the (direction-)problem graphically or numerically? Please show me your attempt to be able to help you.
 
notsoclever said:

Homework Statement


A car is moving toward north with a speed of 35 km/h. A truck travels toward west with a speed of 42 km/h.
Which is the speed of the caravan according to the car's driver?
Does "caravan" refer to the truck? In British English, a caravan is a trailer. In American English, a caravan is a collection of vehicles (also animals) that are traveling as a group.

The truck is roughly SW of the car. Perhaps the question could be rephrased as "how fast is the distance from the car to the truck changing?"
notsoclever said:

Homework Equations

The Attempt at a Solution


The solution given by the book is 15 m/s with direction south-west, but I get the solution of 15 m/s with direction north-west and I cannot get the reason.
Can you help me with this?
Thanks
 

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