Vector projection

krazydog

New member
Joined
Oct 25, 2011
Messages
14
I have a story problem that i cant seem to get..

an object moves along a track in the direction of the positive x axis while being pulled by a cable that makes an angle of \(\displaystyle \theta\) from the positive x-axis.
If \(\displaystyle \theta = 25^0\) and you want a 10 pound force applied to the object in the direction of the positive x axis what must the tension of the cable be? Use vector projection.

This is what i have came up with.

\(\displaystyle v = cos 25^0 i + sin25^0 j\)

w1 = \(\displaystyle ( \frac {u . v}{ ||v||^2})v \) = \(\displaystyle (F . V ) V\)

projF = \(\displaystyle 10( sin 25^0) V\)

w1 = \(\displaystyle 4.2261 ( cos25^0 + sin 25^0)\)

\(\displaystyle w1 = 4.2261\)

w2 = F - w1 ?

\(\displaystyle 10 j + 4.2261( cos25^0 i + sin 25^0 j)\)


\(\displaystyle = 3.8301 i - 11.786 j \)


I dont even think i did this right?

Please help me. Im not getting this. =(
any help in simple terms would be very thankful!
 
I have a story problem that i cant seem to get..

an object moves along a track in the direction of the positive x axis while being pulled by a cable that makes an angle of \(\displaystyle \theta\) from the positive x-axis.
If \(\displaystyle \theta = 25^0\) and you want a 10 pound force applied to the object in the direction of the positive x axis what must the tension of the cable be? Use vector projection.

This is what i have came up with.

\(\displaystyle v = cos 25^0 i + sin25^0 j\)

w1 = \(\displaystyle ( \frac {u . v}{ ||v||^2})v \) = \(\displaystyle (F . V ) V\)

projF = \(\displaystyle 10( sin 25^0) V\)

w1 = \(\displaystyle 4.2261 ( cos25^0 + sin 25^0)\)

\(\displaystyle w1 = 4.2261\)

w2 = F - w1 ?

\(\displaystyle 10 j + 4.2261( cos25^0 i + sin 25^0 j)\)


\(\displaystyle = 3.8301 i - 11.786 j \)


I dont even think i did this right?

Please help me. Im not getting this. =(
any help in simple terms would be very thankful!

Assuming this is a 2-D problem:

If the tension in the cable is T, then,

T * cos(25°) = 10

solve for T
 
Why cos and not sin?

What does the following statements tell you:

you want a 10 pound force applied to the object in the direction of the positive x axis

and

moves along a track in the direction of the positive x axis while being pulled by a cable that makes an angle of
6_2554a2bb846cffd697389e5dc8912759.png
from the positive x-axis
 
Top