What is the Average Speed of a Car on a 100 Minute Trip?

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Homework Help Overview

The problem involves calculating the average speed of a car over a trip consisting of three segments with varying speeds. The car travels at different speeds for specified durations, and the challenge is to determine the average speed for the entire trip.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the formula for average speed and the displacement calculation. There is confusion regarding how to eliminate the variable v from the equation. Some question the units of the provided average speed value, while others speculate about the implications of the average speed being 33.33.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the average speed calculation. Some have offered insights into the relationship between the speeds and the average, while others express uncertainty about the elimination of the variable v.

Contextual Notes

There is a lack of explicit values for v, which complicates the discussion around the average speed. Participants are also navigating the constraints of the problem as presented in a homework context.

cmkc109
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Homework Statement



A car travels at a speed v (km/h) for 40 minutes, then at a speed v/2 for 40 minutes, and finally at a speed v/3 for 20 minutes. What is the average speed for the trip

Homework Equations



avg v = displacement / time

The Attempt at a Solution



40v + 20v + 20/3 v = displacement
time = 40+ 40+ 20 = 100minutes

The answer given is 33.33
but, how do you cancel out the v.. I'm confused :(
 
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the average velocity is (5/9)*v
 
what are the units of the 33.33
 
i don't remember :/ but in general, how to solve this question?
 
you can't eliminate the v unless it gives you a value for it. the only thing i can think of is that 33.33 is the average time per journey of the car. if it is asking for the average speed then v must have been 60 km/h.
 

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