Physics-Vectors Homework Help

  • Thread starter bluefire90
  • Start date
  • Tags
    Homework
In summary, plane 1 taxies with a speed of 11.3 m/s due north while plane 2 taxies with a speed of 7.6 m/s in a direction 22.2° north of west. The magnitude of the velocity of plane 1 relative to plane 2 is 10.98 m/s and the direction is 320º counterclockwise from north. The direction of plane 2 relative to plane 1 is 140º counterclockwise from north.
  • #1
bluefire90
7
0
Two airplanes taxi as they approach the terminal. Plane 1 taxies with a speed of 11.3 m/s due north. Plane 2 taxies with a speed of 7.6 m/s in a direction 22.2° north of west. What is the direction of plane 1 relative to plane 2? Give the angle counterclockwise relative to the north. What is the direction of plane 2 relative to plane 1?

*I solved for magnitude first then velocity*

What is the magnitude of the velocity of plane 1 relative to plane 2?

To solve for the magnitude I found the vector components of plane 2:

Y component: 7.6 * sin(22.2°) = 2.87 m/s
X component: 7.6 * cos(22.2°)= 7.04 m/s
To find the final magnitude of the resultant vector I just used the pythagorean theorem after subtracting the plane 1 components FROM the plane 2 components.

2.87 m/s - 11.3 m/s = -8.43 m/s
7.04 m/s - 0 m/s = 7.04 m/s

Now to find the magnitude I used the pythagorean theorem.
Using the pythagorean theorom I got 10.98m/s as the relative velocity. This velocity is the same for plane 2 relative to plane 1.

To find the direction of plane 1 to plane 2 I just used the arctan formula

arctan (7.04/-8.43) = -39.86°
Now since its counterclockwise from north I just added to 360 to get 320° which is the correct answer.

I can't seem to figure out how to get the direction of plane 2 relative to plane 1 however and I've tried using the law of cosines and various other methods but I'm not sure where to go. Any help would be appreciated.
 
Physics news on Phys.org
  • #2
Welcome to PF!

Hi bluefire90! Welcome to PF! :wink:
bluefire90 said:
I can't seem to figure out how to get the direction of plane 2 relative to plane 1 however and I've tried using the law of cosines and various other methods but I'm not sure where to go. Any help would be appreciated.

Yes, your results look fine.

And the direction of plane 2 relative to plane 1 is just the opposite of the direction of plane 1 relative to plane 2 (V21 = -V12).

So the opposite of 320º is … ? :smile:
 
  • #3
Thanks for the help! Although I did try -320.0° and it wasn't correct! I thought the same thing though
 
  • #4
bluefire90 said:
Thanks for the help! Although I did try -320.0° and it wasn't correct! I thought the same thing though

There's no such thing as -320º :rolleyes: … that would be 40º

but that isn't the opposite of 320º anyway, is it? :wink:

(just draw it! :smile:)
 
  • #5
Haha my background in geometry is pretty weak but if I looked at it logically and drew it the opposite might be 130?
 
  • #6
140 degrees i mean
 
  • #7
Help! You're confusing me! :biggrin:

Yes, the opposite angle is always the original ± 180º. :smile:
 
  • #8
haha thanks for the help! Wow that problem just made a lot more sense!
 

1. What is a vector in physics?

A vector in physics is a mathematical representation of a physical quantity that has both magnitude and direction. It is typically represented by an arrow, with the length of the arrow representing the magnitude and the direction of the arrow representing the direction of the quantity.

2. How do you add vectors in physics?

In order to add vectors in physics, you must first determine their components (magnitude and direction) and then use the Pythagorean theorem and trigonometry to find the resultant vector. The magnitude of the resultant vector is equal to the square root of the sum of the squares of the individual vector components, and the direction can be found using inverse tangent.

3. What is a scalar in physics?

A scalar in physics is a physical quantity that only has magnitude and no direction. Examples of scalars in physics include mass, temperature, and time.

4. How do you subtract vectors in physics?

To subtract vectors in physics, you can use the same method as adding vectors. However, when subtracting vectors, you must change the direction of the vector being subtracted by 180 degrees. This is equivalent to adding a vector with the same magnitude but opposite direction.

5. What is the difference between distance and displacement?

Distance is a scalar quantity that refers to the total length of a path traveled, while displacement is a vector quantity that refers to the change in position from the starting point to the ending point. Distance can be positive or zero, but displacement can be positive, negative, or zero, depending on the direction of motion.

Similar threads

  • Introductory Physics Homework Help
Replies
25
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
8K
  • Introductory Physics Homework Help
Replies
9
Views
700
  • Introductory Physics Homework Help
Replies
5
Views
2K
  • Introductory Physics Homework Help
2
Replies
38
Views
1K
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
196
  • Introductory Physics Homework Help
Replies
16
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
850
  • Introductory Physics Homework Help
Replies
23
Views
2K
Back
Top