Simple machines make work easier by changing the magnitude or direction of a force, allowing one to use less force to do the same amount of work. They achieve this typically in three ways: by increasing the distance over which the force is applied, by changing the direction of the applied force, or by multiplying the input force to produce a greater output force. This principle of force multiplication is known as mechanical advantage. For example, a lever allows lifting a heavy object with less effort by increasing the distance over which the force is applied, while a pulley can change the force direction, making it easier to lift loads. Although simple machines don't reduce the total work done (force × distance remains constant), they change how the work is done to make tasks feel easier and more efficient. The six classic simple machines are the lever, wheel and axle, pulley, inclined plane, wedge, and screw, each altering force in ways that reduce the effort needed to perform physical tasks.