Forces...

[skyhuck]

If one ton is suspended from the pulley, an equivilant force is acting on the fixed point to keep it motionless.

So you are correct - a one ton load on either leg will place a load of 2 tons onthe pulley - doubling it

 

That simply cannot be true, if you added more lines and pulleys would it keep increasing???????

[Matthew Storrs]

Surely, because A is fixed then its force is not entirely taken by the pulley, if a ton was hanging on either side of the pulley then the force on the pulley would be 2 ton, but in this case I would say the force on the pulley would only be 1 ton as the rope is fixed on p the base of the tree on other other side.

[Matthew Storrs]

How much force is being exerted on point A. Is it still 1 ton? Or 2? If your trying to winch a vehicle (point A) out I'm sure you get twice as much pull on the vehicle if you add a pulley into the system so the rope doubles back on itself....

[Dan Earp]

[Pete Mctree]

That simply cannot be true, if you added more lines and pulleys would it keep increasing???????

 

It is correct, so if you keep adding pulleys & lines you will snap your anchor point.

 

Think, we use this function to a positive use I.e when we set up mechanical advantage with a 5 to 1 pulley system to pull a tree over. Make sense?

[crackoff]

Point A is 1 ton, simply put, the effort to hold the weight is equal to its weight. If point A was up the tree, and where the weight is, was the branch and the lowering item was on point B, then with point B being one ton, the other two point (if all was equal) would be 0.5 ton each.

[Matthew Storrs]

Yes you are correct- I confused myself for a moment there!

[Arbtech Tree Services]

If one ton is suspended from the pulley, an equivilant force is acting on the fixed point to keep it motionless.

So you are correct - a one ton load on either leg will place a load of 2 tons onthe pulley - doubling it

 

Correct, the diagram shows forces in a state of equilibrium.

i.e. the force either side of the pulley must be equal but opposite (from Newton's third law of motion)

Therefore the force on the top pulley is indeed the sum of the forces either side (2 tons)

 

That simply cannot be true, if you added more lines and pulleys would it keep increasing???????

 

I assume you mean if more pulleys are introduced on the fixed side to give a mechanical advantage?

If so, the force either side of the pulley is still equal as the load is still at rest. Even if the lines and pulleys are attached between the load and suspension point you are still balancing the downward force of the 1 ton load with a downward force of 1 ton whatever mechanical advatage you employ to acheive it.

 

Hope that's clear as mud.

 

Now, if i'd paid a little more attention at school i wouldn't be a bloody tree monkey:thumbdown:

 

Regards,

 

Steve.

[CJM]

It is correct, so if you keep adding pulleys & lines you will snap your anchor point.

 

Think, we use this function to a positive use I.e when we set up mechanical advantage with a 5 to 1 pulley system to pull a tree over. Make sense?

 

That doesn't make any sense, if you add more pulleys the weight will be distributed throughout those pulleys

[Arbtech Tree Services]

Sorry, slow typing, was responding to a few posts back!

 

It is correct, so if you keep adding pulleys & lines you will snap your anchor point.

 

Think, we use this function to a positive use I.e when we set up mechanical advantage with a 5 to 1 pulley system to pull a tree over. Make sense?

 

When pulling over a tree you are winching from a fixed anchor point with a enormous load. As you winch away you are you are simply increasing the pulling load to match the anchor load with the intention that the tree you are pulling will give way first.

 

Regards,

 

Steve.