AP Physics B Kinematics Presentation #48

The New Jersey Center for Teaching and Learning
26 Jun 201206:39
EducationalLearning
32 Likes 10 Comments

TLDRThis script explains the process of finding the direction of the resultant vector C from two given vectors, A and B. Vector A is 8 units north, and vector B is 4.5 units east. Using geometry, the script demonstrates two methods to determine the angle ฮธ between the resultant vector C and the x-axis. The first method involves using the tangent of ฮธ as the opposite over the adjacent side, resulting in ฮธ being 60 degrees. The second method finds ฮธ by considering the angle between A and C, also yielding a 60-degree angle with the x-axis. Both methods confirm that the resultant vector makes a 60-degree angle with respect to the x-axis.

Takeaways
  • ๐Ÿ“ The script discusses the direction of the resultant vector when adding two vectors, A and B.
  • ๐Ÿ” Vector A is described as having a magnitude of eight units and pointing north.
  • ๐Ÿ“ Vector B is described as having a magnitude of four point five units and pointing east.
  • ๐Ÿ“ˆ The tail-to-tip method is used to add the vectors, resulting in a new vector C.
  • ๐Ÿงญ The magnitude of the resultant vector C was previously calculated, but the focus here is on its direction.
  • ๐Ÿ“ The direction of C with respect to the x-axis is sought using trigonometric methods.
  • ๐Ÿ“ˆ The angle between the vectors is determined using the tangent of the angle, which equals the opposite side over the adjacent side in a right triangle.
  • ๐Ÿ“Š The first method involves finding the angle between vector A and the x-axis by using the inverse tangent of the ratio of A's magnitude to B's magnitude.
  • ๐Ÿ“‰ The second method involves finding the angle between vector B and vector A, and then subtracting it from 90 degrees to find the angle with the x-axis.
  • ๐Ÿ”ข The calculations result in an angle of 60 degrees for the direction of the resultant vector C with respect to the x-axis.
  • ๐Ÿ”š The script concludes that the resultant vector makes an angle of 60 degrees with the x-axis, confirmed by two different methods.
Q & A
  • What are vectors A and B in the given scenario?

    -Vector A is eight units north, and vector B is four point five units east.

  • How is vector A represented in the script?

    -Vector A is represented in red and has a magnitude of eight units in the north direction.

  • What is the method used to find the resultant vector C?

    -The tail-to-tip method is used to add vectors A and B to find the resultant vector C.

  • What is the magnitude of the resultant vector C?

    -The magnitude of C is not explicitly stated in the script, but it can be calculated using the Pythagorean theorem from the components of A and B.

  • What is the purpose of finding the direction of the resultant vector C?

    -The direction of the resultant vector C is found to determine the angle it makes with respect to the x-axis.

  • How is the angle ฮธ related to vectors A and B?

    -The angle ฮธ is found using the tangent function, where ฮธ equals the inverse tangent of the ratio of the magnitudes of A and B.

  • What are the two methods described in the script to find the angle of the resultant vector C with respect to the x-axis?

    -The first method uses the geometric property that the angles between the vectors are equal. The second method involves finding the angle between vector A and the resultant vector C, and then subtracting it from 90 degrees.

  • What is the calculated angle ฮธ using the first method?

    -Using the first method, the angle ฮธ is found to be 60 degrees using the inverse tangent of 8 units over 4.5 units.

  • What is the calculated angle ฮธ using the second method?

    -Using the second method, the angle ฮธ is initially found to be approximately 30 degrees, and then adjusted to 60 degrees by subtracting from 90 degrees.

  • Why are two different methods used to verify the angle of the resultant vector C?

    -Two different methods are used to provide verification and ensure the accuracy of the result, showing that the angle of the resultant vector C with respect to the x-axis is indeed 60 degrees.

  • What is the significance of the angle between the x-axis and the resultant vector C?

    -The angle between the x-axis and the resultant vector C is significant as it provides the direction of the combined effect of vectors A and B in the context of a coordinate system.

Outlines
00:00
๐Ÿ“š Vector Addition and Resultant Direction

This paragraph explains the process of adding two vectors, A and B, where A is 8 units north and B is 4.5 units east. The script describes drawing these vectors using the tail-to-tip method and finding the resultant vector C. It then discusses two methods to find the direction of C with respect to the x-axis. The first method involves using the geometry properties of the angles formed by the vectors, while the second method involves calculating the angle between vector A and C. Both methods conclude that the angle of the resultant vector C with respect to the x-axis is 60 degrees.

05:02
๐Ÿ” Determining the Resultant Vector's Angle with the X-axis

In this paragraph, the focus is on determining the angle that the resultant vector C makes with the x-axis. It clarifies that since the y-axis is perpendicular to the x-axis, and vector A is parallel to the y-axis, the angle between A and C is 30 degrees. By subtracting this from 90 degrees, the angle between C and the x-axis is found to be 60 degrees. This paragraph reinforces the conclusion from the previous paragraph, confirming that the resultant vector C makes an angle of 60 degrees with the x-axis.

Mindmap
Keywords
๐Ÿ’กResultant Vector
The 'resultant vector' is the vector that sums up the effects of two or more vectors when they are added together. In the video, the resultant vector C is the sum of vectors A and B, which are being combined to find the overall direction and magnitude of the combined force. The script describes the process of finding the magnitude of C and then its direction with respect to the x-axis.
๐Ÿ’กTail-to-Tip Method
The 'tail-to-tip method' is a graphical technique used to add vectors by placing the tail of one vector at the tip of another and then drawing the resultant vector from the original tail to the new tip. In the script, this method is used to visually represent the addition of vector A and B to find the resultant vector C.
๐Ÿ’กMagnitude
The 'magnitude' of a vector refers to its length or size, which is a scalar quantity. The script mentions finding the magnitude of the resultant vector C after adding vectors A and B, which is an essential step in vector addition to understand the overall effect of the combined vectors.
๐Ÿ’กDirection
The 'direction' of a vector is the angle it makes with a reference axis, typically the x-axis in a Cartesian coordinate system. The video's main focus is on determining the direction of the resultant vector C with respect to the x-axis, which is crucial for understanding the orientation of the combined forces.
๐Ÿ’กTangent
The 'tangent' function, often abbreviated as 'tan', is a trigonometric function that relates the angle of a right triangle to the ratio of the opposite side to the adjacent side. In the script, the tangent function is used to calculate the angle ฮธ between the vectors A and C, which is essential for finding the direction of the resultant vector.
๐Ÿ’กInverse Tangent
The 'inverse tangent', or 'arctan', is the inverse function of the tangent and is used to find the angle when the ratio of the opposite side to the adjacent side is known. The script uses the inverse tangent to calculate the angle ฮธ by taking the ratio of the magnitudes of vectors A and B.
๐Ÿ’กTrigonometry
Trigonometry is a branch of mathematics that deals with the relationships between the sides and angles of triangles, particularly right-angled triangles. The script applies trigonometric principles to find the angle of the resultant vector, using the tangent and inverse tangent functions to relate the angles and sides of the triangles formed by the vectors.
๐Ÿ’กCartesian Coordinate System
The 'Cartesian coordinate system' is a mathematical framework used to describe positions on a plane using ordered pairs of numbers, typically represented by the x and y axes. The script uses this system to define the directions of vectors A and B and to calculate the angle of the resultant vector with respect to the x-axis.
๐Ÿ’กPerpendicular
Two lines or vectors are 'perpendicular' if they intersect at a right angle, which is 90 degrees. In the script, the concept of perpendicularity is used to understand the relationship between the x and y axes and to calculate the angle between the resultant vector C and the x-axis.
๐Ÿ’กRight Angle
A 'right angle' is an angle of exactly 90 degrees, which is the angle formed when two lines are perpendicular to each other. The script mentions the right angle in the context of the relationship between the x-axis and the vector A, which is parallel to the y-axis, to find the angle of the resultant vector C with respect to the x-axis.
Highlights

Introduction to the problem of finding the direction of the resultant vector of two given vectors.

Vector A is defined as eight units north.

Vector B is defined as four point five units east.

Illustration of vector addition using the tail-to-tip method.

Resultant vector C is introduced as the sum of vectors A and B.

Magnitude of resultant vector C was previously calculated.

Current focus is on determining the direction of vector C with respect to the x-axis.

Explanation of using geometric properties to find the angle between vectors.

Method 1 involves finding the angle between vector A and the x-axis.

Method 2 involves finding the angle between vector B and the x-axis.

Use of the tangent function to calculate the angle theta.

Calculation of theta as the arctan of the ratio of vector A to vector B.

Theta is found to be 60 degrees using the first method.

Theta is calculated to be 30 degrees using the second method.

Explanation of the relationship between the angles to find the resultant's direction.

Final conclusion that the resultant vector makes a 60-degree angle with the x-axis.

Demonstration of two different methods arriving at the same conclusion.

Transcripts
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