Actually I am in high school I just want to confirm that whether two figures of this question possible:

Question is :

A car is moving along a straight line OP.It moves from O to P in 18 seconds and returns from P to Q in 6 seconds , where OP = 360 metres and OQ = 240 metres.What are the average velocity and average speed of the car is going (a) From O to P and back to Q?

My physics teacher made this figure from the question:

by My teacher

and I this figure is also right:

by me

But When I solve the above Question by first figure I got Average speed of 20 m/s and 40 m/s from 2nd figure.

Which one is correct?

(When I ask my Question to my physics teacher , He said "First one is correct,Second one doesn't make any sense")


closed as off-topic by ACuriousMind, Brandon Enright, Kyle Kanos, Emilio Pisanty, Danu Aug 22 '14 at 18:34

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  • $\begingroup$ Well, yes, you're not told what the distance from P to Q is. If the PQ distance was 600m the second drawing would be correct. I have to say that my immediate assumption was that the PQ distance is 120m and that the first diagram is correct, and I imagine this is what your teacher meant. $\endgroup$ – John Rennie Aug 22 '14 at 17:06
  • $\begingroup$ Your interpretation of the question is perfectly acceptable, and your teacher is being daft if he says the second one doesn't make sense. Did he say why it doesn't make sense? $\endgroup$ – Pranav Hosangadi Aug 23 '14 at 0:00
  • $\begingroup$ The information given is on the face of it ambiguous. Yet - if your diagram was correct the average speed of the car over the second trajectory would be 100 m/s. The acceleration required to cover 600 m in 6 seconds is beyond the capability of any car in existence. So looking at all the information in the question, your diagram is not physically possible. Sorry - today the teacher wins. $\endgroup$ – Floris Aug 23 '14 at 1:00

Your numbers would naturally be different because the setups are different. Both setups are technically correct, but the one drawn by your physics teacher is more conventional, as the third letter alphabetically is generally understood to lie somewhere between the other two.

  • $\begingroup$ But When Car Returns from P, it doesn't mention in question that Q is behind the O or in the middle of O and P $\endgroup$ – J.Smith.JJJ Aug 22 '14 at 15:29
  • $\begingroup$ @J.Smith.JJJ My bad - you're right. I'm fixing this in my answer. $\endgroup$ – Dave Coffman Aug 22 '14 at 15:36

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