Practical Machines

In parcice, it is difficult to get an ideal machine. Friction exists between all surfaces of contacts of movable parts. some of the work done by the effort is utilized to overcome frictional resistance. Hence, the useful work done in lifting the load is reduced resulting in the reduction of efficiency.

Let P be the actual effort required.

P_i be the ideal effort required.

W be the actual load to be lifted.

W_i be the ideal load to be lifted.

Then , P - P_i is called effort lost in friction. And W - W_i is called frictional resistance.