What Speed is Required for a Car to Average 60 km/h Over a 200 km Journey?

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Homework Help Overview

The problem involves a car traveling a total distance of 200 km, with a specified speed for the first half of the journey and a requirement to average 60 km/h overall. Participants are exploring how to determine the necessary speed for the second half of the journey based on the given conditions.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are calculating the time taken for the first segment of the journey and attempting to relate it to the average speed requirement. There are questions about whether the time for the second segment can be determined without knowing the speed.

Discussion Status

Some participants have provided calculations for the time taken for the first segment and are attempting to set up equations to find the speed for the second segment. There is an ongoing exploration of how to connect the known values to find the unknown speed.

Contextual Notes

Participants are working under the constraints of needing to average a specific speed over the total distance, which influences their calculations and assumptions about time and speed relationships.

Loppyfoot
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Homework Statement


A car making a 200-km journey travels 50 km/h for the first 100 km. How fast must the car go in the second 100 km to average 60 km/h?


Homework Equations


There is the average velocity equation, and also the average speed equation.
(delta x)/(delta t) = average velocity
average speed = total distance/total time


The Attempt at a Solution


50 = 100/t
to get the time? Do I need to do that?
Then should I do the same for the next one?
 
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t1 = 100/50 s
t2 = 100/v s
Total distance is given.
Average velocity is given. Total time t = t1 + t2.
Substitute these values in the relevant equation to find v.
 
Ok, so ,
t1 = 2s
t2 = 100/v s

The total distance is 200km. The average velocity for the 2nd portion is 60km/h. I do not have t2, because I don't have v. I am confizzled.
 
Total time t = 200m/60 km/h.
t1 is known. Find t2. Then find v.
 

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