AnswersPrecalculusDot Product and Work

Dot Product and Work Answers

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1
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Two vectors of lengths 5 and 8 have a dot product equal to –20. Which is true about the vectors?

A
The angle between the vectors is acute.
B
The angle between the vectors is obtuse.
C
They point in the same direction.
D
They point in opposite directions.
2
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x · y =

A
320
B
240
C
3888/5
D
5184/5
3

Let u = ⟨5, –7⟩ and v = ⟨2, 1⟩. What is u · v?

A
–2
B
1
C
3
D
17
4

Given |u| = 8, |v| = 6, and the angle between is θ = 40°, find the approximate value of u · v.

A
10.72
B
14.77
C
36.77
D
48.77
5

xy =

A
10
B
40/3
C
216/5
D
162/5
6

Two vectors with magnitudes of 6 and 9 have a dot product equal to –27.Find the angle between the vectors.

A
150°
B
120°
C
60°
D
30°
7

Which pair of vectors is orthogonal?

A
⟨3, –5⟩ and ⟨6, –10⟩
B
⟨2, –3⟩ and ⟨9, –6⟩
C
⟨–2, 3⟩ and ⟨–6, –4⟩
D
⟨–5, 4⟩ and ⟨–4, –2⟩
8

He is pulling 400 feet over level ground by exerting a constant 25-pound force on the bar that makes an angle of 30° with the ground. How much work is Thomas doing to pull the wagon?

A
10,000 foot-pounds
B
8,660 foot-pounds
C
7,070 foot-pounds
D
5,000 foot-pounds

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