2. Simple Machine
A machine can be defined as a tool that makes our work
easier by helping us overcome a larger force (called
load) by applying lesser force (effort).
A complex machine consists of two or more simple
machines working together.
There are six types of simple machines: lever, wheel
and axle, pulley, inclined plane, screw, and wedge.
3. 1. Lever
A lever is rigid rod arranged in such a manner that it
can move freely around a fixed point. It consists of
three parts.
Fulcrum: This is fixed point around which the rod
moves.
Load: It is the force that needs to be applied on the rod
in order to perform a task.
Effort: It is the force that needs to be applied on the rod
in order to perform a task.
4. First-class lever
Levers in which the fulcrum is located between the load
and the effort are called first-class or class one levers.
Examples- a pair of scissors, a see-saw, and a crowbar.
5. Second-class lever
Levers in which the load is located between the fulcrum
and the effort are called second-class or class two
levers.
Examples- a wheelbarrow, a bottle opener, and a nut
cracker.
6. Third-class lever
Levers in which the effort is located between the
fulcrum and the load are called third-class or class
three levers.
Examples- a stapler, a pair of tongs, and a fishing rod.
7. 2. Wheel and Axle
A wheel and axle consists of a wheel rigidly attached to
a rod (called axle). When the wheel is rotated, the axle
also rotates.
Examples of a wheel and axle are a screwdriver, a
doorknob, and the steering wheel of a car.
8. 3.Pulley
A pulley consists of a wheel with a grooved rim and a
rope, a chain, or a belt running around the grooves.
The wheel rotates around a stationary axle.
A pulley can of two types: fixed and movable.
9. In a fixed pulley, the
axle of the pulley is fixed
to some kind of support
such as a hook or a wall,
and one end of rope is
attached to the load.
It is used to lift a bucket
of water from a well and
to raise a flag to the top
of a flagpole.
10. In a movable pulley, the
axle is not fixed to any kind of
support. It is free and movable.
The load is directly attached to
the pulley.
This pulley helps to lift heavy
loads with lesser effort than a
fixed pulley.
A crane uses both fixed and
movable pulleys to lift heavy
loads.
11. 4. Inclined plane
A slope or a flat surface raised at an angle to move
heavy loads with less
effort is called an
inclined plane.
Examples- ramps in
the hospital and slides
in a playground.
12. 5. Wedge
A wedge is formed when two inclined planes are joined
together such that one end is sharp and the other is
blunt.
It is used to cut things.
Examples- knife and axe
13. 6. Screw
A screw is another type of an inclined
plane. It is formed when an inclined
plane wraps around a straight rod-like
structure.
A screw has a spirally grooved
surface with a pointed end. It is used
to hold things together.
