00:03
In this example, we have a plane that goes along two straight paths.
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Initially, it goes a distance of 40 kilometers at an angle 60 degrees north of east.
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We draw our compass here, northeast, southwest.
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And then after that, it goes a distance of 30 kilometers 15 degrees north of east.
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So that's what i've drawn here with the first part of our path being a and the second part being b.
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So the resulting displacement vector, which we're going to call r in green here, is going to be the sum of a and b.
00:47
And we want to figure out what the magnitude of r is and also what angle it makes with the horizontal in our coordinate system here.
01:00
Okay.
01:01
So to do this, we're going to have to figure out what the components of r are.
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And if we remember, when we add two vectors together, we can get the resulting vector just by adding the components of each vector together.
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So that means we can get r sub x just by adding the x components of a and b.
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And we can get r sub y by adding the y components of a and b.
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So we just need to go work out what these components are.
01:31
And then we can look at calculating the magnitude and the direction of our vector.
01:36
So for a, let's start there.
01:42
We're going to find the x and y components by using our trigonometric functions sign and cosine.
01:50
Specifically, we have a right triangle formed by a that looks something like this.
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And we're going to be able to get the y component of a over here by using the sign function because the sign relates the opposite and hypotenuse, or the opposite side in the hypotenuse of this triangle to the angle.
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And we'll be able to get the adjacent side with the cosine, because the cosine is going to relate the adjacent side and the hypotenuse to the angle.
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So a sub x is going to be given by a, the magnitude of our vector, or the hypotenuse of this triangle, times the cosine of 60 degrees.
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And a sub y will be given by a times the sign of 60 degrees.
02:53
So for a sub x, this is just going to come out to 20 meters.
02:57
And for a sub y, we should get 34 .6 meters.
03:04
And that's just when we're using a is equal to 40 kilometers.
03:07
So actually, we should make sure we put kilometers here.
03:14
So let's get rid of those, put kilometers.
03:23
Now, for the x and y components of b, we're going to do something identical.
03:26
So again, our vector b, we can form a right triangle with it and our axes in our coordinate system here.
03:41
And we'll be able to get the adjacent side to our angle with the cosine and the opposite side with the sign.
03:50
So bx is going to be b times the cosine of 15 this time.
04:00
And b sub y is going to be b times the sign of 15 degrees.
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So we should put 15 degrees here too.
04:09
Okay.
04:11
And if we go ahead and plug those into our calculator, where b is 30 kilometers, we should get 29 meters for b sub x and 7 .7 meters, set it again.
04:28
Kilometers, kilometers, 29 kilometers and 7 .77 kilometers for b sub y...