# Travelled vs Displacement

• Dec 5th 2011, 05:45 PM
TKHunny
Travelled vs Displacement
At a recent mathematics competition, the following problem was presented:

"If Steve travels three miles due west and then four miles due north, how far has he travelled from his original position?"

The answer given as correct was "five miles". I disagreed strongly and suggested they also take "7 miles" as a correct response.

The intent is clear enough, but the wording is not.
• Dec 5th 2011, 06:22 PM
skeeter
Re: Travelled vs Displacement
This is what happens when problem authors take a math perspective instead of a physics one.

I see the same thing with problems dealing with velocity and speed.
• Dec 6th 2011, 08:36 AM
HallsofIvy
Re: Travelled vs Displacement
TKHunny, I disagree. If the problem had said "How far has he travelled" then I could see "7 miles" as the correct answer. But the problem specifically says "How far has he travelled from his original position" (emphasis mine). He is now 5 miles from his original position so he has travelled 5 miles from his original postition.

(And I don't see how that has anything to do with "physics" or "math" perspectives.)
• Dec 6th 2011, 11:33 AM
skeeter
Re: Travelled vs Displacement
Quote:

Originally Posted by HallsofIvy
TKHunny, I disagree. If the problem had said "How far has he travelled" then I could see "7 miles" as the correct answer. But the problem specifically says "How far has he travelled from his original position" (emphasis mine). He is now 5 miles from his original position so he has travelled 5 miles from his original postition.

(And I don't see how that has anything to do with "physics" or "math" perspectives.)

it would have been clear if the word "displacement" (a physics term) was used in the question instead of the words "how far"