## Average Speed vs. Average velocity

Do you think that average speed and average velocities are usually the same for something in motion?
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 Recognitions: Homework Help Generally, they are synonyms, but velocity is usually used in the context of physics, I guess.

 Quote by radou Generally, they are synonyms, but velocity is usually used in the context of physics, I guess.
Ya I mean in Physics.

Are they the same? what are the differences?

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## Average Speed vs. Average velocity

I guess there's no difference, except that you usually don't use the term 'speed' in physics.

 Quote by radou I guess there's no difference, except that you usually don't use the term 'speed' in physics.
Thanks

I have one more question, to find the instantaneous speed between lets say 0 and 3 seconds using a distance vs. time graph. I first draw the line fo best fit then I would find the slope right?

 Quote by caprija Do you think that average speed and average velocities are usually the same for something in motion?
It is like comparing apples and pears, they are completely different. One is a scalar the other is a vector quantity.
 Actually, the average speed is the $$\frac{total distance travelled}{total time taken}$$, while average velocity is $$\frac{total displacement}{total time taken}$$. Remember, the displacement can be zero when the distance is not.

 Quote by MeJennifer It is like comparing apples and pears, they are completely different. One is a scalar the other is a vector quantity.
ok so i'm confused now, when we're talking about something in MOTION is the average speed and the average velocity usually the same?

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 Quote by neutrino Actually, the average speed is the $$\frac{total distance travelled}{total time taken}$$, while average velocity is $$\frac{total displacement}{total time taken}$$. Remember, the displacement can be zero when the distance is not.
Hm, could you clarify what you meant by that?

 Quote by radou Hm, could you clarify what you meant by that?
It is possible to have an average velocity of zero, for example.

(You travel at 5 m/s for 2 sec and then you travel at -5 m/s (backwards) for 2 sec)

...and not so with speed (it is a scalar quantity).

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 Quote by Omega_6 It is possible to have an average velocity of zero, for example. (You travel at 5 m/s for 2 sec and then you travel at -5 m/s (backwards) for 2 sec)
I know, but I still don't understand the statement above. Nevermind.
 I wrote: "I do think that average speed and average velocity are usually the same for something in motion because it's still measuring time. The only diffference is that when calculating the velocity, you're calculating the rate at which the object changes it's postition." does that sound about right?

 Quote by radou I know, but I still don't understand the statement above. Nevermind.
Went offline for some time...What exactly did you not understand?
 Speed is a scalar quantity. If we designate forwards as positive movement and backwards as negative movement. I can run back and forth at 1m/s and arive where I started and my speed would still be 1m/s. Now if we are using velocity, it is a VECTOR quantity. This means that you need to indicate MAGNITUDE and DIRECTION. If you were to run 30,000 miles forward and then 30,000 miles backwards in 3 hours, your speed would be $$v=\frac{60000miles}{3hours}=\frac{20000miles}{hour}$$ BUT if you were to give velocity... $$\vec{v}=\frac{(30000miles)+(-30000miles)}{3hours}=\frac{0miles}{3hours}=\frac{0miles}{hr}$$ Get it? Notice the arrow above v to designate whether it is a scalar quantity of a vector quantity.. $$\vec{v}=velocity$$ $$v=speed$$

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 Quote by Checkfate ...BUT if you were to give velocity... $$\vec{v}=\frac{(30000miles+(-30000miles)}{3hours}=\frac{0miles}{3hours}=\frac{0miles}{hr}$$ Get it? Notice the arrow above v to designate whether it is a scalar quantity of a vector quantity.. $$\vec{v}=velocity$$ $$v=speed$$
If you are so 'aware' of the difference between vector and scalar quantities, then you should be more careful when writing equalities.

 Quote by Checkfate Speed is a scalar quantity. If we designate forwards as positive movement and backwards as negative movement. I can run back and forth at 1m/s and arive where I started and my speed would still be 1m/s. Now if we are using velocity, it is a VECTOR quantity. This means that you need to indicate MAGNITUDE and DIRECTION. If you were to run 30,000 miles forward and then 30,000 miles backwards in 3 hours, your speed would be $$v=\frac{60000miles}{3hours}=\frac{20000miles}{hour}$$ BUT if you were to give velocity... $$\vec{v}=\frac{(30000miles)+(-30000miles)}{3hours}=\frac{0miles}{3hours}=\frac{0miles}{hr}$$ Get it? Notice the arrow above v to designate whether it is a scalar quantity of a vector quantity.. $$\vec{v}=velocity$$ $$v=speed$$
Yes, Thanks I get it.

But the question is really confusing, are they usually same or not?
 If you're moving with a constant velocity (speed is constant, direction is constant), then the magnitude of average velocity = average speed. In such a case, the dist-time graph will always be a straight line.