• Support PF! Buy your school textbooks, materials and every day products Here!

Vectors Magnitudes and Angles (Respect to the X Axis)

  • Thread starter FAJISTE
  • Start date
57
0
1. Homework Statement

a) If Vx = 18.00 units and Vy = -15.50 units, determine the magnitude of V.
b) Determine the angle of V with respect to the x-axis.

2. Homework Equations



3. The Attempt at a Solution

Yeah, Part B is pretty much the only one I don't get .

a) Answer is 23.75
b) I'm not too sure about what the whole "respect to the x-axis" means. The angle does lie in the fourth quadrant, so I assumed the answer is to do 360 degrees - the angle (i got 40.73) and get 319.27 but that didn't work. I'm down to one try for the answers, so I have to get this one right.

Thanks!
 
a) If Vx = 18.00 units and Vy = -15.50 units, determine the magnitude of V.

Magnitude = sqrt ( x^2 + y^2)

=> Magnitude = sqrt ( [(18).(18)] + [(-15.5)(-15.5)] )
=> Magnitude = sqrt (324 + 240.25)
=> Magnitude = sqrt ( 564.25)
=> Magnitude = 23.75

With part B I get the same answer as you using:

tan^-1 (y /x)

tan^-1 (15.5/18)

=> Angle = 40.73 degrees
 
57
0
Yeah, that answer is incorrect. I don't get what it means by respect to the x axis
 
If you want to measure it with respect to the x axis it means that you start on the x - axis and move counter clockwise to your angle. I assume?
 
57
0
Ya, that gives me 360 - 40.73 = 319.27, which was wrong :(
 
Hmmm. What answer is given (assuming an answer is given)?
 

rl.bhat

Homework Helper
4,433
5
Wright the angle as -40.73 degree. Because angle in clockwise is taken as negative.
 
57
0
Are you sure? I have one last try and I don't wanna get it wrong!
 

rl.bhat

Homework Helper
4,433
5
I think so.
 
57
0
im scared to try iot :(
 
57
0
can anyone confirm -40.73?
 
1
0
Yes, -40.73 is what I get too.

This means the angle is 40.73 degrees below the horizontal axis.
 

Related Threads for: Vectors Magnitudes and Angles (Respect to the X Axis)

  • Last Post
Replies
8
Views
35K
Replies
12
Views
26K
Replies
7
Views
16K
  • Last Post
Replies
2
Views
4K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
5
Views
13K
Top