MACHINES

MACHINE: -

A machine is a device by means of which work can be performed easily or in a convenient manner.

A machine can be used:

To lift heavy loads by applying little force.

To enlarge magnitude of force

To increase rate of work done

To change the direction of force

Examples of simple machines are: Lever, pulley, inclined plane, wedge, screw etc.

EFFORT OR POWER: -

The power directly applied to a machine to lift a load is called Effort or Power. It is denoted by ‘P’.

LOAD OR WEIGHT: -

The weight lifted by a machine is called Load. It is denoted by ‘W’.

MECHANICAL ADVANTAGE: -

The ratio of weight (load) lifted by a machine to the force (effort) applied on a machine is called mechanical advantage of the machine.

Greater the value of mechanical advantage of a machine, easier is the work done.

Mathematically,

M.A = load/effort

OR

M.A = W/P

UNIT: -

It has no unit.

INPUT: -

Amount of work done on a machine by a given effort (force) is called input of a machine.

Input = effort x distance through which effort acts

OR

Input = P x d

OUTPUT: -

Amount of work done by a machine on the load (weight) is called output of the machine.

Output = load x distance covered by the load

OR

Output = W x D

EFFICIENCY: -

The ratio of output of a machine to the input of machine is called its efficiency.

h = output/input

h = (W x D) / (P x d)

Efficiency in %:

h = (W x D) / (P x d) x100

UNIT: -

It has no unit.

IDEAL MACHINE: -

An ideal machine is a hypothetical machine whose output is equal to its input.

For an ideal machine

Output = Input

Efficiency of an ideal machine is 100% because there is no loss of energy in an ideal machine due to friction or any other means that can waste useful energy.

M.A of an ideal machine is d / h.