Question

Measuring Displacements (page 330)
8. Is the following sentence true or false? Five blocks south is an
example of a displacement.
9. Compare and contrast distance and displacement.
10. What would your total displacement be if you walked from your
front door, around the block, and then stopped when you reached
your front door again?
a. one block
b. two blocks
c. the entire distance of your trip
d. zero
Combining Displacements (pages 330–331)
11. A vector is a quantity that has both
and
.
12. Circle the letter of each answer that could describe the magnitude
of a vector.
a. length
b. direction
c. amount
d. size
13. To combine two displacements that are in opposite directions, the
magnitudes
from one another.
For questions 14 and 15, refer to the figure below.
14. The magnitudes of the two displacement vectors are
and
.
15. Because the two displacements are in opposite directions, the
magnitude of the total displacement is
.
16. Circle the letter that answers the question. What is the displacement
of a cyclist who travels 1 mile north, then 1 mile east, and finally
1 mile south?
a. 3 miles east
b. 1 mile north
c. 3 miles south
d. 1 mile east
17. The vector sum of two or more other vectors is called the

Answer 1

Here are the answers:

8. True — "five blocks south" gives both magnitude and direction, so it is a displacement.

9. Distance is a scalar (only how much ground was covered; path length, always ≥ 0). Displacement is a vector (has magnitude and direction; equals straight-line change in position from start to finish and can be zero if you return to the start).

10. d. zero — if you end up at your front door again, your net displacement is zero.

11. magnitude and direction.

12. a, c, d (length, amount, size can describe magnitude; direction does not).

13. are subtracted from one another (i.e., take the difference of their magnitudes).

14–15. I don’t have the figure, so I can’t give the specific numbers. In general, if the two magnitudes are A and B and they are opposite in direction, the magnitude of the total displacement = |A − B|.

16. d. 1 mile east — the north and south displacements cancel, leaving 1 mile east.

17. resultant (the resultant vector).