Clothes Dryer Motion
Question:
How do the drying machine work based on the effect of centripetal
force? Is it true that there is no force called centrifugal force
i.e. it is a virtual force? When we put the clothes in the drying
machine, they initially lie at the bottom of the drum. Once we
turn on the machine the clothes will be suspending inside the
drum. How are they suddenly loose contact with the drum? When
they are not touching the drum, how can they have forces acting
on them?
Thanks!
Answer:
The clothes are subject to the force of gravity and the force of
the drum wall. Before the drum rotates these forces cancel
themselves out with the clothes lying on the bottom as you say.
When the drum begins to rotate, friction between the piece of
clothing and the drum aided by the protrusions on the drum wall,
cause the piece of clothing to be carried up the side of the
drum. The centripetal acceleration provided by the drum forcing
the piece of clothing into a curved path, tends to hold the
clothing against the drum wall. At some point the centripetal
acceleration is overcome by the component of gravity directed
away from the drum wall so the clothing falls down to the bottom
of the drum again to repeat the process.
Because there are usually several pieces of clothing in the
dryer at the same time, there are always some falling from the
upper half of the drum into the lower half. This creates the
illusion that the clothes are suspended in the drum away from the
wall. Try running the dryer with a single face cloth in it to see
what I mean. It will ride up the drum wall to a point, then fall
back to the bottom to be carried up again.
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JDJ