# Is there a difference between mean speed and average speed ?

1. Apr 25, 2009

### mahela007

Is there a difference between "mean speed " and "average speed"?

Is there a difference between mean speed and average speed? The words "mean" and "average" seem to mean the same thing.

2. Apr 25, 2009

### Staff: Mentor

Re: Is there a difference between "mean speed " and "average speed"?

The words are the same.

3. Apr 25, 2009

### rcgldr

Re: Is there a difference between "mean speed " and "average speed"?

You may be thinking of "median" which is different. Assuming a "sample" rate based on time, over some fixed time interval, it woudl be the speed at which 1/2 the time in the interval was spent below or at the speed and the other have above or at the speed. Median is more useful in statitics where the samples are discrete and not continuous.

4. Apr 26, 2009

### mahela007

Re: Is there a difference between "mean speed " and "average speed"?

That seems to be the case.
I was told that mean speed is (v+u)/2 (v is final velocity and u is initial)
while average speed is simply distance/time

5. Apr 26, 2009

### ImAnEngineer

Re: Is there a difference between "mean speed " and "average speed"?

That's correct, but there's no distinction to be made between mean and average. I thought mean is chiefly used in British, and average in American English.

6. Apr 26, 2009

### xxChrisxx

Re: Is there a difference between "mean speed " and "average speed"?

Thats some good observation on your part, I never noticed that Americans tend to use avg. and Brits use mean. I just read avg and mean as one and the same.

I suppose its technically less ambiguous to use mean. in reality everyone knows what you are on about anyway

"Take the average speed"
"Erm which average? mean median or mode"

7. Apr 26, 2009

### ZapperZ

Staff Emeritus
Re: Is there a difference between "mean speed " and "average speed"?

Er... hello?

If "mean velocity" is defined as (v+u)/2, while average velocity is the total distanced traveled over time, then they are NOT identical, and it is no longer simply "Americans versus British" usage!

The definition of "mean velocity" is very strange, unless it is for a very specific situation of a uniform, constant acceleration. I would tend to go with Russ and say that they are the same thing, and that this "definition" here needs to be looked at more carefully to see if it is valid.

Zz.

8. Apr 26, 2009

### ImAnEngineer

Re: Is there a difference between "mean speed " and "average speed"?

I don't think they are... but I'm not a native speaker so I might be wrong. In my language we use the same word for both.

9. Apr 26, 2009

### rcgldr

Re: Is there a difference between "mean speed " and "average speed"?

The "mean" usage is probably assuming constant acceleration, and in that case it's equal to distance over time.

There's also "mean" as in "mean value theorem", where the mean point is the point at which the tangent to the curve has the same slope as the slope from start point to end point. In the case of constant acceleration, velocity versus time is a straight line, and the mean value could be any point on the line, so it doesn't mean much in that case (I know bad pun).

10. Apr 26, 2009

### xxChrisxx

Re: Is there a difference between "mean speed " and "average speed"?

Good point. I've always used them interchangably without a second thought about the situation.