what is a machine

what is a machine.A machine is a device on which a force applied at one point, is used to overcome a force at another point.

A machine is a device, which simplifies works by magnifying the effort.

Principle of machines:
It states that a small force (effort) moves over a large distance to produce a bigger force that moves the load over a small distance.

Effort: Is the force applied at one point of a machine to overcome the load.

Load: Is the force, which is overcome by the machine using the effort.

Mechanical Advantage (M.A):
This is the ratio of load to effort.

image 264

Note:-Mechanical advantage has no units.
-M.A is the number of times the load is greater than the effort. Alternatively, it gives the number of times the machine magnifies the effort.

Velocity ratio (V.R):
This is the ratio of the distance moved by the effort to the distance moved by the load

image 265

Note: It is the ratio of the velocity of the effort to the velocity of the load in the same time.
It is independent of friction.

Efficiency (𝜼):
This is the ratio of work output to the work input expressed as a percentage.

image 266

The efficiency of a machine system is always less than 100% because of;

Friction in the moving parts of the machine.
Work wasted in lifting useless weights like movable parts of the machine.

The efficiency can be improved by;
Oiling or greasing the movable parts.
Using lightweight materials for movable parts.