AnswersPrecalculusDot Product and Work

Dot Product and Work Answers

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Given vectors u = ⟨2, –3⟩ and v = ⟨1, –1⟩, what is the measure of the angle between the vectors?

A
11.3°
B
78.9°
C
92.2°
D
101.3°
2
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Consider vectors u = ⟨2, 1⟩ and v = ⟨4, –1⟩ with the angle between them equal to 40°. What are the scalar projections uv and vu?

A
uv = 1.33 and vu = 1.33
B
uv = 1.33 and vu = 3.16
C
uv = 1.71 and vu = 1.33
D
uv = 1.71 and vu = 3.16
3

Given vectors u and v, with |u| = 10 and |v| = 12, and the angle between the vectors is 53°, what is u · v?

A
0.72
B
1.20
C
13.24
D
72.22
4

What is the relationship between vectors u = ⟨1, 0⟩ and v = ⟨0, –3⟩?

A
The vectors form an acute angle of approximately 48°.
B
The vectors form an acute angle of approximately 71°.
C
The vectors are orthogonal because the angle between them is 90°.
D
The vectors form an obtuse angle of approximately 132°.
5

A force of 10 newtons acts in a direction 75° above horizontal, moving an object 15 meters from (0, 0) to (15, 0). What is the work done by the force?

A
2.59 joules
B
3.88 joules
C
38.82 joules
D
150.00 joules
6

A force acts in the direction ⟨4, 2⟩, moving an object along a straight path from (2, –4) to (10, 1). How much work is done by the force?

A
12 joules
B
42 joules
C
48 joules
D
78 joules
7

Consider vectors u and v, where u = ⟨1, –1⟩ and v = ⟨1, 1⟩. What is the measure of the angle between the vectors?

A
0°
B
60°
C
90°
D
180°
8

Suppose u · v = 0. Which vectors could represent u and v?

A
u = ⟨3, 4⟩ and v = ⟨4, –3⟩
B
u = ⟨3, 4⟩ and v = ⟨–4, –3⟩
C
u = ⟨–3, 4⟩ and v = ⟨4, –3⟩
D
u = ⟨–3, –4⟩ and v = ⟨–4, –3⟩
9

Given vectors u = ⟨–3, 2⟩ and v = ⟨2, 1⟩, what is the measure of the angle between the vectors?

A
7.1°
B
60.3°
C
119.7°
D
172.9°
10

Which pair of vectors is orthogonal?

A
u = ⟨–3, 2⟩ and v = ⟨–2, 1⟩
B
u = ⟨1, 5⟩ and v = ⟨–5, 1⟩
C
u = ⟨2, 1⟩ and v = ⟨–4, 3⟩
D
u = ⟨2, 3⟩ and v = ⟨3, 1⟩

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