Magnitude of moment about axis (Space Truss)

[U1021981]

Homework Statement

Determine the magnitude of the moment of the force F about the axis CA of the tripod
ABCD, if F = {40i -30j -100k}N.

Image attached.

2. The attempt at a solution

Based on a similar question I found in the textbook my method to solve this question:

Find U_CA = r_CA/r_CA = (-2/√8)i + (2/√8)j

Find M_CA = U_CA.(r_DC?? * F)

However, I am unsure if the finding the position vector r_DC is correct?

Am I going about this the right way?

Please help.

Thanks,

Tim

 

[SammyS]

Homework Statement

Determine the magnitude of the moment of the force F about the axis CA of the tripod
ABCD, if F = {40i -30j -100k}N.

Image attached.

2. The attempt at a solution

Based on a similar question I found in the textbook my method to solve this question:

Find U_CA = r_CA/r_CA = (-2/√8)i + (2/√8)j

Find M_CA = U_CA.(r_DC?? * F)

However, I am unsure if the finding the position vector r_DC is correct?

Am I going about this the right way?

Please help.

Thanks,

Tim

Here's your image:

First of all your r_CA must be incorrect. Look closely. Point A is 1.5 m from the origin on the y-axis. Point C is 2 M from the origin on the x-axis.