Assignment 9 QA

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course Mth 164

1:15 pm3/10/15

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Question: `q001. Sketch the points (2,3) and (9,14) on a set of coordinate axes. Give the x and the y displacements from (2,3) to (9,14).

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Your solution:

If I understand correctly to get from (2, 3) to (9, 14) we move as follows:

9 - 2 = 7

14 - 3 =11

(7, 11) between the 2 points.

confidence rating #$&*: 2

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Given Solution:

`aAs shown in Figure 75, the x displacement is from 2 to 9, a displacement of 9 - 2 = 7, while the y displacement is from 3 to 14, a displacement of 14 - 3 = 11. The arrows represent the direction of the displacements, from the initial point (2, 3) to the terminal point (9, 14).

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Self-critique (if necessary):

OK

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Self-critique Rating: OK

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Question: `q002. In the preceding example we saw that the x and y displacement from from (2,3) to (9,14) are 9-2 = 7 and 14-3 = 11. Sketch an arrow which originates at (2,3) and terminates at (9,14), with the point of the arrow at the terminating end. If we were to sketch a geometrically similar arrow, having the same slope, orientation and length as the preceding, but starting at the point (-2, 5) at what point would the arrow terminate? Note that we can and should really incorporate information from the physics introductory problems.

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Your solution:

Since the displacement was 7 horizontally and 11 vertically we must increase (-2, 5) by this displacement to make a similar arrow at different points. So:

-2 + 7 = 5

5 + 11 = 16

So the end point would be:

(5, 16)

confidence rating #$&*: 3

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Given Solution:

`aOriginating at (-2,5) the arrow will displace 7 units in the x direction and 11 units in the y direction. Starting at x = -2 the arrow will displace 7 units in the x direction to end up at x = -2 + 7 = 5. Starting at y = 5 the arrow will displace 11 units in the y direction and end up at y = 5 + 11 = 16. The arrow therefore originates at (2,-5) and terminates at (5, 16).

If we sketch the same arrow starting from the point (-2, 5) then it will again displace 7 units in the x direction, ending up at x = -2 + 7 = 5, and 11 units in the y direction, ending up at y = 5 + 11 = 16. As shown in Figure 58 the arrow terminates at the point (5, 16).

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Self-critique (if necessary):

OK

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Self-critique Rating: OK

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Question: `q003. We say that the displacement of 7 units in the x direction and 11 units in the y direction is a vector, represented by the arrows used in the preceding problems and denoted using 'pointy braces' as < 7, 11 >. If we apply this vector, starting this time at the origin, at what point do we end up?

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Your solution:

Well starting at the origin which I understand to be (0, 0) then we would end at the point (7, 11).

confidence rating #$&*: 2

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Given Solution:

As shown in Figure 40 this vector takes us from the origin (0,0) to the point (7, 11).

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Self-critique (if necessary):

OK

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Self-critique Rating: OK

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Question: `q004. If we start from the terminal point of the vector in the preceding exercise and sketch a new vector having x displacement 3 and y displacement -8, at what point do we end up? Sketch the arrows representing these two vectors, the first running from (0,0) to (7,11) and the second from that point to its terminal point.

Now sketch a vector from directly from (0,0) to the terminal point of the second vector.

How can the x displacement of this new vector be calculated from the x displacements of the first two vectors? Answer the same question for the y coordinates.

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Your solution:

If we start at terminal point (7, 11) and use the displacement <3, -8> then we would arrive at the point:

7 + 3 = 10

11 + -8 = 3

(10, 3)

I believe the 3rd vector can be found by adding the first 2 together and starting at the origin and ending at the point found from the addition of the 2 points.

confidence rating #$&*: 2

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Given Solution:

`aAs shown in figure 11, the second vector runs from (7, 11) to (7 + 3, 11 + (-8) ) = (10, 3).

The vector from the initial point of the first vector to the terminal point of the second therefore runs from (0, 0) to (10, 3), as shown in Figure 72.

It should be clear from the calculations done above and from the sketches that the x displacement of the new vector is calculated by adding the x displacements of the original two vectors, and that the same strategy works for the y displacements.

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Self-critique (if necessary):

OK

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Self-critique Rating: OK

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Question: `q005. In what sense can we say that the vector <10,3> is the sum of the two vectors <7, 11> and <3, -8>?

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Your solution:

Since the x values:

7 + 3 = 10

And the y values:

11 + -8 = 3

This is the point we arrive at.

confidence rating #$&*: 3

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Given Solution:

`aThe x coordinate of the new vector to is 10, which is the sum 7 + 3 of the x coordinates of the two vectors. The y coordinate of the new vector is 3, the sum 11 + (-8) of the y coordinate of the two vectors. In this respect it is the sum.

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Self-critique (if necessary):

OK

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Self-critique Rating: OK

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Question: `q006. Access the site

http://vhmthphy.vhcc.edu/ph1introsets/default.htm

and choose Set 5, Vectors. Click in turn on Problems 1 - 9 and see if you can solve these problems. Solutions are given and are generalized and many are accompanied by figures. If you can't immediately solve them, study the solutions and learn to solve them. Explain the solution to the first problem.

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Your solution:

The problem for number one is:

What are the x and y components of a vector whose length is 2 and whose angle with the positive x axis is 87 degrees?

The solution is:

The x component is 2 cos( 87 deg) = .1.

The y component is 2 sin( 87 deg) = 1.99.

I’m not sure I understand why this is the answer or how to explain the solution.

This is one explanation given on the page:

The components of a vector of magnitude v which makes angle `theta with the positive x axis, as measured counterclockwise from the axis, are vx = v cos(`theta) and vy = v sin(`theta).

If I understand this then the vectors x value is found by, v cos (theta) where theta is the given angle and v is the magnitude. We can also understand this for v sin(theta) to find the y value as well.

confidence rating #$&*: 2

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Given Solution:

`aIn case clarification is needed, displacement is just movement through a distance and in a certain direction. The vector (3, -8) of the preceding problem (and figur 72) corresponds to a displacement of 3 units in the x direction and -8 units in the y direction.

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Your solution:

This does not seem to fit the given problem.

confidence rating #$&*: 2

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Given Solution:

`aThis completes this q_a_. Click once more for a message on completing the remainder of this assignment.

Complete Assignment 9, including Class Notes, text problems and Web-based problems as specified on the Assts page.

When you have completed the entire assignment run the Query program. Submit SEND files from Query and q_a_.

end program

001. Radian measure and the unit circle.

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Your solution:

I’m not sure what this is referring to so I’ve decided to move along.

confidence rating #$&*: 0

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Given Solution:

`aGoals for this Assignment include but are not limited to the following:

1. Know the definition of the radian.

2. Relate coordinate positions on the unit circle to angular displacement and to arc displacement.

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Self-critique (if necessary):

I will keep these goals in mind.

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Self-critique Rating:

OK

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Self-critique (if necessary):

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Self-critique rating:

OK

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Self-critique (if necessary):

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Self-critique rating:

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&#Your work looks very good. Let me know if you have any questions. &#