Physics Review QuestionUnit:
mechanicsYear:
1996 Question#:
2Question:
A student walks 40. meters along a hallway that heads due north, then turns and walks
30. meters along another hallway that heads due east. What is the magnitude of the
student's resultant displacement(1
) 10. m(2
) 35 m(3
) 50. m(4
) 70. mWhat is this question really asking?
Explanation by: Ajemo H [ Return to question menu
]Answer 1
10. m INCORRECT Displacement is a vector quantity between two points (the shortest distance between two points) The only way to get an answer of 10. meters is to subtract 30. meters east from 40. meters north. 10. meters only tells us how much further north the student travelled. return to top
Answer 2
35. m INCORRECT Displacement is a vector quantity between two points (the distance between two points measured in a straight line). 35 m is the answer obtained by averaging 40. meters north and 30. meters east. 35 m is the average distance the student travelled in each direction. Additionally, an answer of 35 m does not have the correct number of significant figures return to top
Answer 3
50. m CORRECT The student's path fortunately consisted of straight lines and right angles. Therefore we can use the pythagorean theorem to find the distance between where the student's path started and stopped. A ^{2} plus B^{2} equals C^{2}. We plug 30. meters east in for A, and 40. meters north for B. 30. meters squared
plus 40. meters squared equals 2500 meters^{2}. Then we take the square root of that number and get 50. meters. That's the length
of the distance between where the student started and where the student ended up.
return to top
Answer 4
70. m INCORRECT We are looking for the distance from where the student started to where the student stopped. An answer of 70. m can be reached by adding 30. meters east and 40. meters north. 70. meters is the total distance the students travelled. But, displacement is the shortest distance from where the student started to where the student finished. Since the student did not travel in a straight line, we can find a shorter distance. return to top
What's this question really asking?
This question is asking if you know the definition of displacement. It is also seeing if you know some basic math (The pythagorean theorm). return to top |

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