Physics question

Ok, not a third gen subject but neither are a chunk of other posts here. I ask here since I know there's a handful of smart engineers and/or engineer types here.

I'm getting ready to make a hoist contraption but need some simple physics help to aid in my rigging. Best way to describe by idea is to ask:

If a beam is suspended by cables mounted to a ceiling (both cables 90* to the ceiling) one cable is 2 ft long and the other cable is 3 feet long. The beam is 5 feet long and weight 50 lbs, cables are attached at the ends of the beam at an even distance from the end of the beam.

Do both cables support the same weight?

I haven't put this to paper yet (trying to get my boy to sleep first). However, thinking about the free body diagram for each point on the beam there's a sine and cosine factor for both ends... It makes me think that each cable will have different tensions, right? Or am I over complicating this and of course both cables support 25 pounds each?

 

No they don’t. Think about if you held the cables yourself. You would be holding the shorter cable with more strength than the longer one.

I need to find some paper to write the force diagrams on. But that’s a good thought experiment.

 

That's what I would think but I kinda wanna know for sure for my design. I kinda like to either experiment with scales to know for sure of work the problem on paper and know for sure that way. It's been 2 years since I have taken physics 2 or a statics class so I have forgotten most of the fundamentals that would help me solve this type of problem.

 

Both cable hangers will have the same load as long as the suspended load on the beam is equal distance from the cable hangers (or in other words if the load is in the middle of the beam).

 

Let's say the 50 lbs is evenly distributed through the beam.

 

So you're saying that both cables are supporting 25 lbs each since they have the same angle to the ceiling?

 

Would still be the same tension or load in each cable.

 

Is this a trick question? In general yes but...... if the cables are attached to the beam very close to center, then the short cable could end up with all the weight with nothing exerted on the longer cable other then it's own weight. But it probably wouldn't hang straight down in that case.

 

The shorter cable that has the the beam higher in the air will take more weight/tension then the longer cable. Only reason i can say this is because i do tandem lifts with cranes and the moment i take a load higher then the other crane i pull more weight on my scale and the other crane loses weight.

 

establish X to the right, and Y up are positive
Beam angles from lower left to upper right
the beam is static. no "X" component.
Figuratively "Cut" the cables. summate "Y" Components; Y1 + Y2 -50 =0
Assume uniform weight for the beam
Center of mass is 2.5 feet along the beam from the left end but due to the angle of the beam, this is (square root of 24)/2 from the left end in the x direction.
Establish that clockwise moment is positive.
summate moments about the left end of the beam
{((Square root 24)/2)*50}-{(square root 24)*Y2}=0
122.47=4.90*Y2
reaction force Y2=25.0000025 LbF in the positive Y direction
therefore Y1 = 24.9999975

Damn near 25 lbs each

 

cant wait for the explanation, cause if its linear pull i cant see how increased length decreases the weight. would this mean that if you shorten your winch cable its load weight changes?
then again im convinced the big ball lands first

 

That’s a statics/dynamics problem . Draw it up and I’ll do the math for ya

 

Never mind. He already did the statics. Listen to this guy.

 

I think the issue is the bean is horizontal, the roof anchor pints are at different heights. If the beam is horizontal, cables support the same weight as long as it’s distributed.

 

Statics is still physics based, just a department of physics really. I did take physics and statics a while back but forgot most of it. Gonna draw up a diagram and dig out my physics book and make up a couple free body diagrams for each cable and replicate what was said above.

 

This is the best thing I’ve read all day. Good on ya. The math never lies

 

Here's a quick drawing of my question...