The six kinds of simple machines Select a lesson
what are the human senses

Define a simple machine
types of machines
explain an inclined plane for children Explain a wedge simple machine
Explain a screw simple machine Explain a lever simple machine
Explain the wheel and axle simple machineWhat is a pulley simple machine
Terminology on simple machines


Asexual Reproduction
Charact' of Living Things
Elements, mixtures, comp.


Needs of Living Things
Nutrients in Food
Rock Cycle
States of Matter
The Five Senses
Water Cycle
The Lever simple machine

The Pulley

Have you seen your school flag being raised before? This is possible with a simple pulley. When you pull down on the rope, the pulley turns and the flag goes up.
Pulleys change the direction of the force.

spur gear and worm gearA pulley is simply a wheel with a groove in it, and a rope in the groove. It is also called a drum or a sheave. The groove is important because it helps to keep the rope in place. It is used to lift up or lower heavy objects. With a pulley, an object to be lifted can be tied to one end of the rope, and a force is applied to the other end by pulling the rope downwards. The downward force turns the wheel with the rope and pulls the load upwards at the other end.

Types of Pulleys
There are three types of pulleys. Each pulley system depends on how the wheel and rope are put together.

Kinds of pulleysFixed Pulley
This is the simplest form of pulleys. Simple pulleys have their axles fixed in place and cannot be moved. The rope moved in the groove of the pulley but the wheel is fixed to one spot. The wheel on your school flag pole is a good example.

spur gear and worm gearKinds of pulleysMovable Pulley
In a movable pulley, (see diagram on the left) the load is attached to the pulley and both of them can move from place to place. In this type, one end of the rope is attached to a fixed point that does not move. With a movable pulley, you need less effort to lift a load. Can you tell how the movable pulley is similar to the Class Two Lever? Both of them have the load between the effort and the fulcrum!

Kinds of pulleysCompound Pulley
This is also called a combined pulley. It is a combination of pulleys designed to make the effort less than half of the weight of the load. This kind is very common at construction sites where cranes lift very heavy steel and concrete objects. One good example of a compound pulley is a Block and Tackle. Click here to see a diagram of the Block and Tackle

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pulley  simple machines