If i ask wat r the application of simple machine some of u will say-----> Simple machines that are widely used include the wheel and axle, pulley, inclined plane, screw, wedge and lever. While simple machines may magnify or reduce the forces that can be applied to them, they do not change the total amount of work needed to perform the overall task.
but actually the application of simple machine is
i) they transfer force from one point to another
ii) They accelerate the rate of doing work
iii) the multiply force