Physics Law in washing machine design

Written by Siti Aishah Che Kar and Syila Izawana Ismail

Nowadays, washing machine is one of the must-have household equipments. But how does the smart machine spin and drain all the water from our clothes? Or what is actually happening during the spinning process? Here comes the scientific explanation. Centrifuge is the word or term that is used to describe the whole process. You can do a very simple experiment at home to understand the centrifuge phenomenon. Take wet clothes and turn the clothes while holding them. You can see the excess water sparking out from the wet clothes. Actually the clothes spin in circle because you force it but the water trapped in clothes retains to move in straight line. Thus the water will fly out from the wet clothes and automatically the clothes will be drier than before. [1]

Thus this concept is applied in the washing machine process. After the rinsing process, the washing machine will be in drain mode automatically where a pump is used to drain all the excess water. Then, the spin mode will take over. In top loader washing machine, the agitator which is a large plastic at the bottom of the drum will spin while in the front loader washing machine, the drum itself will spin. The drum is actually like a big basin that holds our clothes. Usually each washing machine contains two drums which are the inner drum and the outer drum. The clothes are forced to move in circle because the inner drum is spinning but the excess water in clothes still goes straight, turning into water drop. The water drop is small enough to pass through the drum’s tiny holes into the outer drum. This phenomenon is actually relevant to the Isaac’s most famous laws of motion. The First Law of motion states, “A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force.” This simply means that things cannot start, stop, or change direction all by themselves. It takes some force acting on them from the outside to cause such a change [2].

The centrifuge concept is well used in many applications especially in science laboratory as centrifuges to separate things like component in blood or any substances in liquid form. The blood sample will be spin at high speed using centrifuge to separate the blood cell such as plasma and red blood cells. NASA also uses centrifuge concept for testing their astronauts and pilots in psychology test by using human centrifuges to test whether the astronauts are fit for the space ship [3].

References:

[1] http://www.explainthatstuff.com/centrifuges.html

[2] https://www.livescience.com/46558-laws-of-motion.html

[3] https://en.wikipedia.org/wiki/Astronaut_training