A tank attached to a chain is attempting to tow a person
holding the other end of it. The chain is wrapped three times completely
around a metal pole that is permanently anchored. The person pulls with a force
of ten pounds. The tank pulls with a force of ten thousand pounds. Does
the tank pull the chain out of the hands of the person? Show your
Tank Held Back by Strong Man
An inclined plane is a simple machine. A threaded screw is an inclined
plane wrapped around a cylinder. The value of either of these machines
is that they increase the effect of exerting some force. In other words
a pull or push gets more to happen when either is used.
Whenever two items touch there is friction between them. Even when it is
a boat and some water or a car and the road or air, the moving object
reacts. Sometimes the reaction is in the form of heat. When
rope is touching something, the heat generated to pull it past its
starting location depends on how many times it is wound around the other
object. The answer is a number measuring wrapping friction.
The next lines tell how much more you'd have to pull on your end to make a
wrapped rope move if it were pulled the other way, as by a hanging
weight. The increase in force you'd have to use depends on the number of times a
rope or chain completely circles an object,
These values say that if the rope was attached to a one pound weight,
the force you'd need to on the other end of the rope to move it is more
than five hundred pounds for only one wrap. But it would be more than
one hundred fifty-three million pounds of force for three wraps.
|One Wrap ... Multiply by 535.492
|Two Wraps ... Multiply by 286,751
|Three Wraps ... Multiply by 1.53553*108
Light Bulb in a Socket
An ordinary light fixture has a metal thread to match the inclined
plane wrapped around the bulb-base cylinder. Look at the bottom of a
bulb. You will see three complete wraps.