(adsbygoogle = window.adsbygoogle || []).push({}); Moment about an axis - Statics - 3 Dimensional Equilibrium

1. The problem statement, all variables and given/known data

The member is supported by a pin at A and a cable BC. If the load at D is 300, determine the x, y, z components of reaction at these supports.

i.e Find the reactions at A and the tension in the cable BC

2. Relevant equations

Since it is in equilbrium.

[tex]\Sigma F = 0[/tex]

[tex]\Sigma M = 0[/tex]

3. The attempt at a solution

The most confusing part for me, is moment about an axis. (If possible, please tell me, how to find moment about an axis - the direct method and through the vector matrix).

Correct me, if i am wrong.

rBC = 0.3i - 0.6j + 0.2k

|rBC| = 0.7

uBC = 1/0.7 (0.3 i - 0.6j + 0.2k)

TBC = |TBC|/0.7 (0.3i - 0.6j + 0.2k)

Now

[tex]\Sigma Fz = 0[/tex]

[tex] = -300 + Az + TBC(0.2 / 0.7)[/tex]

Az is unknown, so to determine Az - we find moment about the x axis of B.

This will give, Az = 0

[tex]\Sigma Fz = 0[/tex]

[tex]= -300 + TBC(0.2/0.7) = 0[/tex]

TBC = 1050 N.

[tex]\Sigma Fx = 0[/tex]

Ax + 1050(0.3/0.7) = 0

Ax = -450 N

[tex]\Sigma Fy = 0[/tex]

Ay - 1050(0.6/0.7) = 0

Ay = 900N

Thats what i could do max (i think im right), now only moment about Y-axis w.r.t a and moment about Z-axis is left, w.r.t a again. (May and Maz).

Please tell me how to get this part, with 2-3 methods to get moment about an axis (Direct and through matrix).

Thanks a lot =)

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Statics - 3 Dimensional Equilibrium

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**