A simple machine makes the work easier and faster by:

• Increasing the force applied
• Changing the direction of force applied
• Transferring the force from one place to another
• Increasing the speed of a force

A machine is a device when force is applied to it, it makes our work easier, changes the direction of force and enhance the speed of the work.

The two types of simple machines are lever and Pulley.

There are six types of simple machines, they are:

1. Lever
2. Pulley
3. Wheel and axle
4. Inclined plane
5. Screw
6. Wedge

The principal of machine is

Input work = Output work

Or, E x E. d = L x L. d

Where, E = Effort

E. d = Effort distance

L = load

L. d = load distance

\begin{align*}\\ \text {effort} (E) = 100\: N \\ \text {load arm} (Ld) =195\: cm\\ \text {Effort arm} (Ed) = 5\:cm \\ \text {load} (l) = ?\: N \\ \text {we know} \\ \text {accoding to the principle of simple machine} \\ \text {load} \times \text {load arm} &= \text {effort} \times \text {effort distance} \\ \text {or,} \: E\times 195 &= 100 \times 5 \\ \therefore &= \frac {100 \times 5}{195} \\ &= 2.56\: N\\ \end{align*}

Seesaw has the fulcrum F at the centre and thus forms the lever of first class. Let the boy st at a distance X metre from the centre.

\begin{align*} \text {effort} (E) = 50\: kg \\ \text {load arm} (Ld) =1\: m \\ \text {load } (l) = 20 \: kg \\ \text {Effort arm} (Ed) = X\:m \\ \text {we know} \\ \text {accoding to the principle of simple machine} \\ \text {load} \times \text {load arm} &= \text {effort} \times \text {effort distance} \\ \text {or,} \: 50\times 1 &= 20 \times X \\ \therefore X = \frac {50}{20} \\ &= 2.5 m \\ \end{align*}