Pulleys

Most likely levers of some kind were used in very ancient Egypt (5000 BCE), and certainly one could say that they were used/invented well before the ancient Greeks came to the scene.

The Giza Pyramids were constructed using step-walking wooden four-lobe pinion-pulleys with a mechanical advantage of 2.8 (MA=2.8)

This ancient pulley was unknown to the modern world until 27 August 2006.

The design and operation of this pulley is nothing like any pulley known in the modern world.

Google four lobe pinion pulley.

He made it because it took half the weight of the load off

use calculator

Fixed if it weighed as less than you, but a movable pulley wouldn't be helpful here. You'd be best with a pulley with multiple supporting ropes.

When you lift an object, three things happen:

1) The lower extremities take on the weight of both your body and the object being lifted, and..

2) Your center of gravity is offset in front since you must lift the object in front of your body. This forces you to compensate using a change in posture, making more muscles work to lift. (Think of how long you can stand straight, verses how long you can stay in a stooped position.)

3) Since your hands are extended, this essentially uses your hands as a lever against you. (Take a weight, and lift it close to your body and compare it with lifting it with your arm straight out.. you will feel the difference!)

For instance, if I lift a large box, I need to extend my hands at least to the center of the box. My arms are acting as a lever, and my center of balance is moved forward. This places added strain on my body. My legs have also taken on the extra weight of the box.

Pulleys essentially redirect force along the path of the rope. This allows the force to be placed in a way that is easiest for our bodies to apply.

If I use a pulley, my legs are actually under less strain. Also, since I can pull the rope close to my body, the weight is not levered against me, and my center of gravity is only altered minimally. I can then use my body in its most efficient manner to exert the force required to lift the box.

If the pulley is frictionless the angle does not matter, the tension in the rope will be the same on both sides of the pulley.

If there is friction in the pulley however then you want to reduce the friction as much as possible. You do that by creating as large an angle between the two ropes as possible.

A pulley system is made up of a pulley and a rope. A pulley is, in essence, a wheel with a groove going all the way around it so that a rope or a cable can fit in it securely.

One could also run an indented track around a wheel.

The mechanical advantage is a numerical relationship among the sizes of

physical components of the machine. It's constant as long as the sizes

of those parts of the machine are constant.

It depends on how many times the rope 'goes around' the pulleys. If there are 2 ropes 'pulling up' then the mechanical advantage is double. Think about it this way: the tension throughout the rope is constant, so if the object being lifted is 100 pounds, but there are 2 ropes going up from the movable pulley, then each rope has 50 pounds tension on it, but they are the same rope, so you are pulling with 50 pounds force on the rope to create the 50 pounds tension.

Note that the pulley system reduces the amount of force necessary to lift, but the amount of work necessary is the same. Example: if you want to lift the 100 pound weight by 1 foot, you will use 100 foot-pounds of work. With the pulley system as described, you are exerting 50 pounds of force, and must pull the rope 2 feet to lift the weight 1 foot.

A car engine

It acts as torque-multipier by trading distance for effort.(as you know from your basic physics, WorkDone = Force XDistance.

So if you replace a 1:1 arrangement witha 2:1 pulley, you needto pull twice as much rope but with only half the tension - though you will use the same energy overall!

wagons it has to constas of a rope or belt

Ideal mechanical advantage is the mechanical advantage when there is no friction.

It is the mechanical advantage when the efficiency of the pullefy system is 100%. It is a constant for that system of pulleys. Therfore it is not affected by increasing or decreasing the load.

But actual mechanical advantage will be less than this ideal mechanical advantage due to friction. In other words the efficiency will be less than 100 %. If the efficiency is 80%, it implies 20% is wasted due to friction while lifting a load.

If we increase the load the friction also increases and hence the efficiency will decrease with the load.

There are nearly 75,000 species of wasps worldwide, according to scientists.

True

Pulley belongs to one of the class of Simple machines

They are two types of pulleys 1. Fixed pulleys 2. Movable pulleys.

Examples Fixed pulley :

flag poles, sail boats, simple cranes, curtains in theatres, conveyor belt, simple line elevators

Examples Movable pulley :

Cranes , amusement park rides , elevators and cable cars using movable pulleys.

movable pulleys sometimes don't have a directional advantage so you have to pull up and you can't use a weight as the effort and whoever said this its wrong so next time USE THE TEXT BOOK STUPID PERSON sorry about this my friend can be mean.

Compound pulleys are used in a similar manner to a gearbox. You can select the ratio to suit the load and the power source. With the correct pulley combination one man can lift 10 tons from a truck onto a ship without motorised assistance.

we find mechanical advantage of pulley by using principle of lever. according to this moment of effort is equal to moment of moment of load. As in this case effort arm is equal to load arm. so mechanical advantage is equal to one. but we know we can never finish friction between rope used and pulley so mechanical advantage is less than one

blindsshoe laceswellflagpoleWashing machine has pulleys that turn it.

An example of a pulley sytem is a flag pole.

it is easyer to lift

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It doubles your lifting power.

Probably somebody threw a vine over a stick...