Physics Questions About Vector

In summary, Vector A is 3.00 units in length and points along the positive x-axis. Vector B is 4.00 units in length and points along the negative y-axis. Vector C is the vector that Vector B is added to to create X.
  • #36
ehh did a seach on google, since at first I didnt get what you said, now after looking at some pictures I think I get what you mean.

First picture (A + B)
|--->
|
|
\/

Second Picture (A + (-B))
/\
|
|
|
|--->

Third Picture Shift (A) Upwards
/\--->
|
|
|
|

Now Draw the Line
/\--->
|.../
|.../
|../
|/
 
Physics news on Phys.org
  • #37
Precisely!
 
  • #38
so magnitude and direction are still the same though right?

except its positive degrees
 
  • #39
Yes, this is because X and Y are at right angles to each other.
(It is not true in general)
 
  • #40
Note:
The "direction" is not the "same" since it uses positive degrees rather than negative degrees.
 
  • #41
actually the angles different since

[tex]tan = opp/adj[/tex]

so its [tex] tan^-^1 = 3/4 [/tex]
 
Last edited:
  • #42
Nope, the angle between the vector (3,4) and the x-axis has "4" as the opposite side, and "3" at the adjecent side
 
  • #43
(3,4) is (x,y)

so X-Axis is 3
and Y-Axis is 4
 
  • #44
Definitely!
But its angle with respect to the x-axis, is to regard the triangle with hypotenuse up to (3,4), the vertical line segment down to (3,0) (and then along the horizontal to the origin).
What you're looking at is the vector's angle with respect to the y-axis, not with respect to the x-axis.
 
  • #45
Ahh I see you calculate this

/\--->
|.../
|../
|./
|/X

and to calculate that you would have to shift the vectors
.../\
.../.|
../..|
./...|
/X..|

therefore its still [tex] tan = 4/3 [/tex]
 
  • #46
Then we agree?
 
  • #47
yep lol now there's this odd problem that I've been trying to solve but I can't get it. The answers in the back of the book but there's no explanation.

Each of the displacement vectors A and B shown in Figure P3.3 has a magnitude of 3. Graphically find (a) A + B (b) A - B (c) blah blah (d) blah blah

I think If I got one of it I would get the rest.

A is the diagonal line
B is Bolded the vertical line

/\
|.../
|.../
|.../
|../
|./
|/30(degrees)____
 
  • #48
Well, it's just the same procedures really; are you supposed to answer with a diagram or with coordinate values?
 
  • #49
this one isn't hw, i just want to get a better understanding of how to do it. the answers in numbers and there's a degree angle too.

I know how to move it but then you can't do the theorem with this.

...|
...|
^...|
|.../
|.../
|../
|/
----------- >
 
  • #50
True enough, but let's find the coordinates of the skew line (A).
We know that its length is 3, and the angle to the x-axis is 30.
This means that its coordinates is:
[tex](3\cos(30),3\sin(30))[/tex]
You are now able to find the coordinates to for example, the sum of A+B
 
  • #51
umm i did that... i get a different answer from the book

(2.6,1.5)

the other one is three but the same thing can be done to found it
3cos(90),3sin(90)

(0,3)
 
  • #52
(2.6,1.5) looks right;
what does your calculator say when you type in cos(30)?
Multiply that number with 3.
 
  • #53
i get .8660254038

*3 = 2.598076211

How would you get the answer after that?

Rx = Ax + Bx = 2.6 + 0
Ry = Ay + By = 1.5 + 3

Now I add Rx + Ry = 7.1

Answer in book is 5.2m at 60 above x-axis
 
  • #54
HAVE YOU FORGOTTEN PYTHAGORAS?

The resultant vector is:
[tex](\frac{3\sqrt{3}}{2},\frac{9}{2})[/tex]
The length is therefore:
[tex]\sqrt{\frac{27}{4}+\frac{81}{4}}=\frac{\sqrt{108}}{2}[/tex]
 
  • #55
how did u get the resultant vector?
 
  • #56
[tex]\cos(30)=\frac{\sqrt{3}}{2},\sin(30)=\frac{1}{2}[/tex]
(This is a rather well-known relation; you'll it later on)
Hence A has coordinates [tex](\frac{3\sqrt{3}}{2},\frac{3}{2})[/tex]
Summing A with B (coord. (0,3)) yields the resultant vector).
 
  • #57
ahh indeed it does.. this makes sense now :D

yes I learned cos(30) = 3/2 in precalculus the 30-60-90 triangle
 
  • #58
wohoo got B) correct how would you get the degree though?
 
  • #59
How do you think?
 
  • #60
ummm I know all the measurements of the sides yet no angles except that 30 degrees, but its on the outside
 
  • #61
But you know its horizontal and vertical coordinates, right?
How can you calculate the tangent of the angle using that info?
 
  • #62
the figure isn't a right triangle though
 
  • #63
You are to find the resultant vectur's angle to the x-axis; how can you construct a triangle in such a manner that the coordinates you've been given will help you find that angle?
 
  • #64
OOO I got it :D

extend the Line downward so the verticles of the triangle are

[tex] tan^-^1 = 4.5/2.6[/tex]

(0,0) --> (2.6,0) --> (2.6,4.5)
 
  • #65
You should get 60 degrees..
 
  • #66
Yep I got 60 degrees 59.9 i think. Thanks for your help :D

nice i think i got section 3.2 and 3.3 of my textbook down ahah... tommo I will probably ask about projectile motion, hopefully you'll help me again. The textbook leaves out a lot of information. Like it leaves out little steps.
 
  • #67
No problem..
 
  • #68
its an emergency...i really need to know this...

can two vectors representing two different physical quantities be equal?

can force and displacement be equal vectors if they are in same direction and have same magnitude?? doesn't representing different phy. quantities makes them different vectors?
 
  • #69
I hate vectors! I'm in physics A and I don't get it, even though I understand all of the force, energy, and projectile motion stuff.
 
<h2>What is a vector?</h2><p>A vector is a mathematical quantity that has both magnitude (size) and direction. It is usually represented by an arrow pointing in the direction of the vector with its length representing the magnitude.</p><h2>How is a vector different from a scalar?</h2><p>A scalar is a mathematical quantity that only has magnitude and no direction, while a vector has both magnitude and direction. Examples of scalars include temperature, mass, and time, while examples of vectors include velocity, force, and displacement.</p><h2>What is the difference between a position vector and a displacement vector?</h2><p>A position vector is a vector that describes the location of a point in space relative to an origin, while a displacement vector describes the change in position of an object from its initial position to its final position.</p><h2>How are vectors added and subtracted?</h2><p>Vectors can be added and subtracted using the head-to-tail method, where the tail of one vector is placed at the head of the other vector. The resulting vector is the one that connects the tail of the first vector to the head of the second vector.</p><h2>What is the dot product of two vectors?</h2><p>The dot product of two vectors is a mathematical operation that results in a scalar quantity. It is calculated by multiplying the magnitudes of the two vectors and the cosine of the angle between them. It is used to determine the component of one vector in the direction of another vector.</p>

What is a vector?

A vector is a mathematical quantity that has both magnitude (size) and direction. It is usually represented by an arrow pointing in the direction of the vector with its length representing the magnitude.

How is a vector different from a scalar?

A scalar is a mathematical quantity that only has magnitude and no direction, while a vector has both magnitude and direction. Examples of scalars include temperature, mass, and time, while examples of vectors include velocity, force, and displacement.

What is the difference between a position vector and a displacement vector?

A position vector is a vector that describes the location of a point in space relative to an origin, while a displacement vector describes the change in position of an object from its initial position to its final position.

How are vectors added and subtracted?

Vectors can be added and subtracted using the head-to-tail method, where the tail of one vector is placed at the head of the other vector. The resulting vector is the one that connects the tail of the first vector to the head of the second vector.

What is the dot product of two vectors?

The dot product of two vectors is a mathematical operation that results in a scalar quantity. It is calculated by multiplying the magnitudes of the two vectors and the cosine of the angle between them. It is used to determine the component of one vector in the direction of another vector.

Similar threads

Replies
5
Views
742
  • Introductory Physics Homework Help
Replies
2
Views
691
  • Introductory Physics Homework Help
Replies
30
Views
408
  • Introductory Physics Homework Help
2
Replies
44
Views
2K
  • Introductory Physics Homework Help
Replies
13
Views
518
  • Introductory Physics Homework Help
Replies
16
Views
669
  • Introductory Physics Homework Help
Replies
2
Views
802
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
620
  • Introductory Physics Homework Help
Replies
1
Views
261
Back
Top