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

AI Thread Summary
To calculate the average speed of a car on a 100-minute trip, the car travels at varying speeds: v for 40 minutes, v/2 for another 40 minutes, and v/3 for 20 minutes. The total displacement is calculated as 40v + 20v + (20/3)v, while the total time is 100 minutes. The average speed is determined using the formula avg v = displacement / time, leading to an average speed of 33.33 km/h. There is confusion regarding how to eliminate the variable v, with some suggesting that the average speed can only be calculated if a specific value for v is provided. Ultimately, the average speed of 33.33 km/h is derived under the assumption that v is 60 km/h.
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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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