Watch
Announcements
#1
for example

if a sign is hanging off a 12m wooden beam, one end is P and the other end is Q.

The sign hangs 8m from P.

calculate moment of the weight of mass about P and Q

SO FOR THIS I worked it out all correctly where moment about P and Q is 313.6Nm AND 156.8Nm respectively.

what is confusing me is that; wouldn't the moments on each side be equal as the wooden beam is in equilibrium????
0
11 months ago
#2
(Original post by Riannnne)
for example

if a sign is hanging off a 12m wooden beam, one end is P and the other end is Q.

The sign hangs 8m from P.

calculate moment of the weight of mass about P and Q

SO FOR THIS I worked it out all correctly where moment about P and Q is 313.6Nm AND 156.8Nm respectively.

what is confusing me is that; wouldn't the moments on each side be equal as the wooden beam is in equilibrium????
If the beam is in equilibrium, then the sum of the clockwise moments of the forces acting on it will be equal to the sum of the anticlockwise moments of the forces acting on it, about some reference point. You are only considering the moment of one of the forces acting on the beam, and you have used two different reference points.
0
11 months ago
#3
(Original post by Riannnne)
for example

if a sign is hanging off a 12m wooden beam, one end is P and the other end is Q.

The sign hangs 8m from P.

calculate moment of the weight of mass about P and Q

SO FOR THIS I worked it out all correctly where moment about P and Q is 313.6Nm AND 156.8Nm respectively.

what is confusing me is that; wouldn't the moments on each side be equal as the wooden beam is in equilibrium????
P & Q must be supported (?), and their reactions would be determined by / in proportion to the distance of the sign from the points.
As an extreme example, the sign could be hanging off P and the beam has zero mass. The reaction at P would take all the weight of the sign and the reaction at Q would be zero. This is exactly what the moments about P & Q would tell you.
Last edited by mqb2766; 11 months ago
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Have you experienced financial difficulties as a student due to Covid-19?

Yes, I have really struggled financially (66)
17.55%
I have experienced some financial difficulties (108)
28.72%
I haven't experienced any financial difficulties and things have stayed the same (142)
37.77%
I have had better financial opportunities as a result of the pandemic (48)
12.77%
3.19%