Why Is the Average Velocity Zero After the 3rd Lap?

[Chica1975]

Homework Statement

During a race on an oval track a car travels at an average speed of 200km/h. a) How far did it travel in 45.0mins? b) determine its average velocity at the end of its 3rd lap.

Homework Equations

ok I worked out part a of the question and that is fine. But logically I can't figure out why the answer to the second part of the question would be 0. Can anyone explain why the average velocity at the end of the 3rd lap would be 0? thanks

The Attempt at a Solution

 

[Sniperman724]

If I were to guess, I would think that since velocity is a vector, at the end of the third lap, the car would technically be in the same place that it started, thus having no displacement, or since the track is oval, on an x-y plane, the car would have both positive and negative velocities in both the x and y plane, so they would probably cancel each other out.

Still not sure though, sorry

p.s. Sorry If the second one doesn't make much sense, i probably explained it horribly

 

[gneill]

Homework Statement

During a race on an oval track a car travels at an average speed of 200km/h. a) How far did it travel in 45.0mins? b) determine its average velocity at the end of its 3rd lap.

Homework Equations

ok I worked out part a of the question and that is fine. But logically I can't figure out why the answer to the second part of the question would be 0. Can anyone explain why the average velocity at the end of the 3rd lap would be 0? thanks

Average velocity is determined by the total displacement (from a starting position) over the total time. Since the car is right back where it started after every lap, that displacement is zero at that moment.

Average speed is another matter; It takes into account the actual distance traveled rather than the displacement.

 

[Chica1975]

of course - I know this I don't know what I was thinking. Sometimes I just go blank!

Thank you!

 

[Sniperman724]

Average velocity is determined by the total displacement (from a starting position) over the total time. Since the car is right back where it started after every lap, that displacement is zero at that moment.

Average speed is another matter; It takes into account the actual distance traveled rather than the displacement.

Yea, what he said, haha I guess I kinda had that in my explanation, but had a brain fart and forgot about the total displacement over total time.

 

[Chica1975]

:) I got it tho - am so grateful for this forum - never would have made it thru physics without it.

 

[Sniperman724]

haha, me neither, I've gone on here to find any kind of help that I needed and was able to find it almost every time :)