# Magnitude of moment about axis (Space Truss)

## 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 UCA = rCA/rCA = (-2/√8)i + (2/√8)j

Find MCA = UCA.(rDC?? * F)

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

Am I going about this the right way?

Please help.

Thanks,

Tim

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• Q6.35.jpg
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SammyS
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## 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 UCA = rCA/rCA = (-2/√8)i + (2/√8)j

Find MCA = UCA.(rDC?? * F)

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

Am I going about this the right way?

Please help.

Thanks,

Tim
Here's your image: First of all your rCA 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.