After completion of this lesson, student must be able to:

  • Describe mechanical advantage, velocity ratio and efficiency of a simple machine (lever, pulley, wheel and axle and inclined plane).
  • Solve  numerical problems related to mechanical advantage, velocity ratio and efficiency of the simple machines mentioned above.
  • Describe the law of moment in lever with an example.  



Simple machine helps us by magnifying force, accelerating work and by changing the direction of force. This notes gives us the information about machine, its importance, mechanical advantage, velocity ratio.

Types of Simple Machine

A lever is a rigid bar may be straight or bent which is capable of rotating fixed point called fulcrum. A pulley is a metallic or wooden disc with a grooved rim. The rim rotates about a horizontal axis passing through its centre. This note gives us information about types of simple machine.


The law of moment states that “In the equilibrium condition of lever, the sum of the anticlockwise moment is equal to the sum of the clockwise moment”. This note gives us further information about moment of force.