Simple machines are devices that help us do work in an easier way.
Using simple machines, a person can apply less force in a direction that is easier to operate to get the same result.
- Inclined Plane: A gradual sloping surface connecting a higher level to a lower level.
The inclined plane makes it easier to move a heavy object from a lower level to a higher level with less effort.
Ex. Ladder helps us to climb to a higher level easily. Ramps are used to load heavy objects into vehicles.
- Screw: An inclined plane wrapped around a cylinder.
A screw helps to do work with even lesser effort than a simple inclined plane.
Ex. A winding road on a hill is easier to climb than a steep road that joins the bottom of the hill to the top of the hill.
Also, the grooves on a metal screw that run from one end of the screw to another end, make it easier to turn the screw.
- Wedge: An inclined plane with one or two sharp slanting edges.
It helps to push a sharp edge into an object to cut through it or separate it, with less effort.
Ex. A blade of an axe has two inclined planes joined together to make a sharp edge that cuts through wood.
Needle and Knife are also wedges.
- Wheel and Axle: A rod (axle) attached to the centre of a wheel. The wheel and the axle can move each other.
So by applying force to the axle, the wheel can be moved and vice versa. Ex. steering wheel of a car, screw driver, door knob.
- Pulley: A grooved wheel with a rope, belt or chain running over it.
It can be movable or fixed to a support. A fixed pulley helps to change the direction of the applied force.
Ex. A pulley attached to a well helps to lift a bucket of water from the well upwards by pulling the rope downwards.
- Lever: A bar free to move about a point of support called fulcrum.
Depending on the position of the fulcrum, levers are classified into 3 classes.
First Class Lever: Fulcrum is in the middle and the load and the effort are at the ends.
Ex. Scissors, Hammer, See-Saw.
Second Class Lever: Load is in the middle and the fulcrum and the effort are at the ends.
Ex. Bottle opener, Nut cracker, Wheel barrow.
Third Class Lever: Effort is in the middle and the load and the fulcrum are at the ends.
Ex. Tweezers, Tongs.