Types of Simple Machine

Simple machines are of the following types:

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

Lever

A lever is a rigid bar may be straight or bent which is capable of rotating fixed point called fulcrum. In a lever, effort distance and load distance are measured from fulcrum. The distance between fulcrum and load is load distance and fulcrum and effort is effort distance.

Pulley

A pulley is a metallic or wooden disc with a grooved rim. The rim rotates about a horizontal axis passing through its centre.

A pulley can be used in single fixed pulley, single movable pulley or combined form (block and tackle). A single fixed pulley makes our work easier by changing the direction only; mechanical advantage is not gained because value of effort and load distance is equal. But in single movable pulley, mechanical advantage is gained. In a block and tackle, MA and VR are directly proportional with the number of pulleys used. If the number of pulley increases in block and tackle the VR also increases. In the same way MA increases.

VR in pulleys = No. of pulleys used (except in single movable pulley) or number of rope segments that support the load.

We have,
MA = \(\frac{Load}{Effort}\)

Inclined plane

Slanted surface which is used to lift the heavy load by applying less effort is called inclined plane. In this device, the length of slope (l) acts as effort distance and height of slope (h) acts as load distance. The value of length of slope is always greater than value of height of slope; therefore value of VR is always greater than 1.

Input work = E × Ed = E × l (∴ l= length of slope)

Output work = L × L d = L × h (∴ h = height of slope)

VR =\(\frac {l}{h}\)

We have,

MA = \(\frac{Load}{Effort}\)

Wheel and axle

Wheel and axle consists of two coaxial cylinders of different diameters. Some examples of wheel and axle are string roller, screw driver etc. in wheel and axle effort is applied on big cylinder called wheel and load is overcome by small cylinder called axle. The circumference of big cylinder 9wheel) is considered as effort distance and circumference of small cylinder (axle) is known as load distance. Therefore, the calculation of VR in wheel and axle can be done by following formula

VR=\(\frac{circumference \;of \;big \;cylinder}{circumference \;of \;small \;cylinder}\)

Or, VR = \(\frac{2πR}{2πr}\) [∴circumference = 2 πr]

∴ VR = \(\frac{R}{r }\)(R=Radius of big cylinder (wheel) and r=Radius of small cylinder (axle) )

We have,

MA = \(\frac{Load}{Effort}\)