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Two vectors \(\vec{A}\) and \(\vec{B}\) have magnitudes \(A=3.00\) and \(B=3.00 .\) Their vector product is \(\vec{A} \times \vec{B}=-5.00 \hat{k}+2.00 \hat{\imath} .\) What is the angle between \(\vec{A}\) and \(\vec{B} ?\)

Short Answer

Expert verified
The angle is approximately \( 36.9^\circ \).

Step by step solution

01

Understanding the Vector Cross Product

The cross product of two vectors \( \vec{A} \times \vec{B} \) can be calculated using the formula \( |\vec{A} \times \vec{B}| = AB \sin\theta \), where \( \theta \) is the angle between vectors \( \vec{A} \) and \( \vec{B} \), and \( |\vec{A} \times \vec{B}| \) is the magnitude of the cross product.
02

Calculating Magnitude of Cross Product

First, we calculate the magnitude of the vector product \( \vec{A} \times \vec{B} = -5.00 \hat{k} + 2.00 \hat{\imath} \). The magnitude \( |\vec{A} \times \vec{B}| \) is found using \( |\vec{A} \times \vec{B}| = \sqrt{(-5.00)^2 + (2.00)^2} \).
03

Solving for Magnitude

Calculating, we get \( \sqrt{25 + 4} = \sqrt{29} = 5.385 \). So, \( |\vec{A} \times \vec{B}| = 5.385 \).
04

Substituting in Cross Product Formula

Substitute the known values into the cross product formula: \( 5.385 = (3.00)(3.00) \sin\theta \).
05

Solving for the Angle \( \theta \)

We solve for \( \sin\theta \) by dividing both sides by \( 3.00 \times 3.00 \), which is 9: \( \sin\theta = \frac{5.385}{9} \approx 0.5983 \).
06

Finding the Angle Using Inverse Sine

Finally, calculate \( \theta \) using the inverse sine function: \( \theta = \sin^{-1}(0.5983) \).
07

Calculating the Angle

Using a calculator, \( \theta \approx 36.9^\circ \). Thus, the angle between the vectors \( \vec{A} \) and \( \vec{B} \) is approximately \( 36.9^\circ \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Angle Between Vectors
Understanding the angle between vectors is crucial in vector mathematics. When two vectors are positioned in space, the angle between them is the measure of rotation required to align one vector with the other. Mathematically, the angle \(\theta\) between two vectors \(\vec{A}\) and \(\vec{B}\) can be found using their vector product and magnitudes.

The angle is calculated using the sine function from the cross product formula:
  • \( |\vec{A} \times \vec{B}| = AB \sin\theta \)
Here, \( |\vec{A} \times \vec{B}| \) represents the magnitude of the cross product of the two vectors, and \( \theta \) is the angle between the vectors.
By rearranging the formula, you can solve for \( \theta \) using the inverse trigonometric function \( \sin^{-1} \), which will allow you to find the specific angle in degrees or radians that make their sine equal to the calculated value. This is crucial because it helps determine the spatial relationship and orientation between vectors.
Magnitude of Vectors
The magnitude of vectors refers to their length or size, a fundamental property necessary for various calculations. For any vector \(\vec{V}\) in three-dimensional space with components \(V_x\), \(V_y\), and \(V_z\), the magnitude is determined as follows:

  • \( |\vec{V}| = \sqrt{V_x^2 + V_y^2 + V_z^2} \)
This equation gives a scalar value, representing how long or short a vector is, irrespective of direction.

To comprehend vectors \(\vec{A}\) and \(\vec{B}\) given in the exercise, both have magnitudes \(A = 3.00\) and \(B = 3.00\). The magnitudes are crucial inputs in calculating the cross product \( |\vec{A} \times \vec{B}| \) and deriving the angle between them. The cross product itself produces a vector whose magnitude is related to the sine of the angle between the original vectors, hence affecting the calculated angle significantly.
Inverse Trigonometric Functions
Inverse trigonometric functions are essential math tools used to determine angles based on their trigonometric ratios.

For instance, if you know the sine of an angle, the inverse sine function, denoted as \(\sin^{-1}\), can be employed to find the angle itself. This is especially valuable when working with vectors.

In the exercise, the angle between vectors \(\vec{A}\) and \(\vec{B}\) was determined using:
  • \(\sin\theta = \frac{|\vec{A} \times \vec{B}|}{AB}\)
  • \(\theta = \sin^{-1}(\text{calculated value})\)
The inverse sine function effectively "undoes" the sine operation, providing the angle value from its sine counterpart.

Utilizing a calculator or computational tools, students can find the precise angle, ensuring that they accurately interpret physical scenarios involving vector directions and relationships.

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Most popular questions from this chapter

While following a treasure map, you start at an old oak tree. You first walk 825 m directly south, then turn and walk 1.25 \(\mathrm{km}\) at \(30.0^{\circ}\) west of north, and finally walk 1.00 \(\mathrm{km}\) at \(40.0^{\circ}\) north of east, where you find the treasure: a biography of Isaac Newton! (a) To return to the old oak tree, in what direction should you head and how far will you walk? Use components to solve this problem. (b) To see whether your calculation in part (a) is reasonable, check it with a graphical solution drawn roughly to scale.

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Vector \(\vec{A}\) has \(y\) -component \(A_{y}=+13.0 \mathrm{m} . \vec{A}\) makes an angle of \(32.0^{\circ}\) counterclockwise from the \(+y\) -axis. (a) What is the \(x\) -component of \(\vec{A} ?\) (b) What is the magnitude of \(\vec{A} ?\)

Vector \(\vec{A}\) has magnitude 6.00 \(\mathrm{m}\) and vector \(\vec{\boldsymbol{B}}\) has magni- tude 3.00 \(\mathrm{m} .\) The vector product between these two vectors has magnitude 12.0 \(\mathrm{m}^{2} .\) What are the two possible values for the scalar product of these two vectors? For each value of \(\vec{A} \cdot \vec{B},\) draw a sketch that shows \(\vec{A}\) and \(\vec{B}\) and explain why the vector products in the two sketches are the same but the scalar products differ.

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