Average Speed: 30km/hr Explained

Click For Summary

Homework Help Overview

The discussion revolves around calculating average speed for a round trip with differing speeds for each leg of the journey. Participants are exploring why the average speed is not simply the arithmetic mean of the two speeds given.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand the calculation of average speed by considering total distance and total time. Questions are raised about why the average speed cannot be simply calculated as the mean of the two speeds. Some suggest using specific distances to illustrate the concept.

Discussion Status

The discussion is active, with participants providing hints and exploring different interpretations of average speed. There is recognition that the average speed calculation involves more than just averaging the two speeds, and some guidance has been offered regarding the formulation of time and distance.

Contextual Notes

Participants are working under the assumption that the distance for each leg of the trip can be represented with specific values to facilitate calculations, but the exact distances are not provided. There is an emphasis on understanding the implications of varying speeds on average speed.

alex engler
Messages
5
Reaction score
0
If the average speed going to town is 40km/hr, and return at an average speed of 60 km/hr. what is the average speed? why is it not 50 km/hr

Is the answer 30? because he goes 40 km/hr for 1 1/2 hours. etc.
 
Physics news on Phys.org
The average speed is found by dividing the total distance by the total time of travel. (Hint: Find expressions for the time for each leg of the trip in terms of its distance and speed.)
 
You can pretend the distance going to town is 200km. Now find the total distance of there and back, divided by the total time. So you must calculate the total time.

An easy way to understand this is pretend you are planning on going from point A to point B(which is 100km from point A). If you go there at 1000km/hr, it will only take you 6 minutes, and if you go back at .00001km/hr, it will take you a LONG time, so doesn't it make sense that your average speed would be quite low?
 
You are correct that the "average speed" is not the arithetic average ([itex]\frac{v_1+v_2}{2}[/itex]) but any "average" of two numbers has to be between them!
 

Similar threads

Average Speed between two cities
  • · Replies 1 ·
Replies
1
Views
2K
How to calculate average velocity given distance and time?
  • · Replies 6 ·
Replies
6
Views
3K
Average Speed Question for a Train that Accelerates and then Decelerates
  • · Replies 20 ·
Replies
20
Views
3K
Simple Motion Along a Straight Line Problem
  • · Replies 5 ·
Replies
5
Views
14K
What are the average speed formulas needed to solve this problem?
  • · Replies 5 ·
Replies
5
Views
5K
Calculating Walking Speed Based on Average Velocity and Distance Traveled
  • · Replies 6 ·
Replies
6
Views
3K
Motion in One Dimension: The Tortoise and The Hare Race
  • · Replies 10 ·
Replies
10
Views
8K
Average speed? -- Homework problem
  • · Replies 11 ·
Replies
11
Views
5K
Displacement & Average Velocity
  • · Replies 3 ·
Replies
3
Views
2K
Relating Linear and Angular Kinematics
  • · Replies 3 ·
Replies
3
Views
2K