# Average speed with an unknown distance

• yorick
In summary, the conversation discusses the calculation of average speed with an unknown distance. The individual travels from Place A to Place B, with half the time at a speed of 60km/h and the other half at 100km/h. On the return journey, they travel half the distance at 60km/h and the other half at 100km/h. By substituting values for displacement and using the formula for average speed, the average speed for the entire trip is determined to be 75km/h.
yorick
[SOLVED] Average speed with an unknown distance

You travel from Place A to Place B, half the time at a speed of 60km/h and the other half at 100km/h. On the return journey, you travel half the distance at 60km/h, and the other half at 100km/h.

a) What is your average speed from A to B?

b) What is your average speed from B to A (return journey)?

c) What is your average speed for the entire trip?

a) $$\overline{Sp}$$ = (60 + 100)/2 = 80km/h... Easy enough.

b&c)
I just don't know where to start with this.
I tried a displacement vs. time graph but without any actual values for the displacement I didn't know what to do.

I'm not necessarily after an answer for this, but a nudge in the right direction would be greatly appreciated.

Thanks,
Yorick.

Okay so I've been playing around a bit more, substituting values for displacement.

This is for b)

Letting x=100km,
I travel 50km @ 60km/h = 50min = 5/6 h
and 50km @ 100kmh/h = 30min = 1/2 h

Then $$\bar{Sp}$$ = Distance traveled / (t$$_{2}$$ - t$$_{1}$$) right?

So t2 would be 5/6 + 1/2, t1=0

then $$\bar{Sp}$$ = 100 / (4/3)
=75 km/h

Let x=200km
100km @ 60km/h = 100min = 10/6 h
100 km @ 100km/h = 1 h

then $$\bar{Sp}$$ = 200 / (16/6)
=75km /h

Valid reasoning?
PS sorry for bad Latexing, my subscripts came out as superscript so I gave up.

Indeed, it is possible to calculate out .
t= 1/2s/60 +1/2s/100= s/120+s/200
v=s/t = s/(s/120+s/200) = 75km h^-1

c) just easy , A->B = the same distance.
you have the average speeds for both sides...

## What is average speed with an unknown distance?

Average speed with an unknown distance is a calculation used to determine the average speed of an object when the distance traveled is not known. It is usually calculated by dividing the total time taken to travel a certain distance by the total time taken.

## How is average speed with an unknown distance different from average speed?

The main difference between average speed and average speed with an unknown distance is that in the latter, the distance traveled is not known. This means that the distance cannot be used in the calculation, and only the time taken is used to determine the average speed.

## Why is average speed with an unknown distance important?

Average speed with an unknown distance is important in situations where the distance traveled is not known, but the average speed of an object needs to be determined. It is commonly used in scientific experiments and in real-world scenarios such as calculating the average speed of a car in heavy traffic.

## What are the limitations of using average speed with an unknown distance?

One of the main limitations of using average speed with an unknown distance is that it does not provide an accurate measurement of the speed of an object. This is because the distance traveled is not known, and the calculation relies solely on the time taken.

## How can average speed with an unknown distance be calculated?

The average speed with an unknown distance can be calculated by dividing the total time taken by the number of intervals or segments. For example, if a car travels for 2 hours and the time is divided into 4 intervals, the average speed would be calculated by dividing 2 hours by 4 intervals, resulting in an average speed of 0.5 hours per interval.

• Introductory Physics Homework Help
Replies
5
Views
1K
• Introductory Physics Homework Help
Replies
6
Views
953
• Introductory Physics Homework Help
Replies
8
Views
2K
• Introductory Physics Homework Help
Replies
5
Views
957
• Introductory Physics Homework Help
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
10
Views
1K
• Introductory Physics Homework Help
Replies
13
Views
1K
• Introductory Physics Homework Help
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
2
Views
2K
• Introductory Physics Homework Help
Replies
4
Views
1K