How Machines Work?

A machine can make a given task seem easier by reducing the amount of force needed to move an object, by changing the direction in which the force must be applied, or by doing both. A machine decreases the amount of force needed by increasing the distance over which the effort is applied to move the object. The amount of work needed to overcome [[KW]] gravity [[/KW]] and lift a given load always remains the same, but spreading the necessary effort out over a longer distance makes the task seem easier. This is why walking gradually up a gentle slope is easier than walking up a steep slope. The distance walked on the gentle slope is longer, but the effort needed to reach the top is less. A gentle slope is a form of inclined plane.
Applying effort over a greater distance takes more time, and this slows down the speed of work. Some machines can actually speed up a task. They do this by reducing the distance over which the effort is applied. If the distance in the equation defining work (Work = Force × Distance) is reduced, then the force must therefore be increased to keep work constant. Increasing the speed at which a task is performed requires more force than would otherwise be necessary. The wheel and axle and certain types of levers are simple machines that can either speed up a task (requiring more effort) or slow down a task (requiring less effort). The various [[KW]] gears [[/KW]] on a multispeed [[KW]] bicycle [[/KW]] (another complex machine) work in a manner similar to that of the wheel and axle. Some gears require more effort, but they make the bicycle travel faster on flat terrain. Other gears require less effort and are useful for climbing hills.
People use simple machines, such as levers and pulleys, to make manual chores easier. The mechanical energy in a person’s [[KW]] muscles [[/KW]] makes the machine do work. Not all machines use muscle power, however, to do work. A complex machine, such as an airplane engine or an elevator, is made up of many simple machines. Airplane engines and [[KW]] elevators [[/KW]] are not powered by hand. Complex machines often use the energy stored in chemical substances, such as airplane fuel or the energy stored in electricity, to provide the necessary force to do work. An airplane engine uses the combustion, or rapid burning, of airplane fuel to power the engine that turns the propeller. An elevator uses large engines, usually powered by electricity, to pull cables that raise and lower the elevator car. Electricity also powers the levers that help open and shut the elevator doors.