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A three-child operation

It took three children to operate this merry-go-round. One child sat on each end and the third child pushed it around and around as fast as possible.


We quickly learned that if we sat on the plank between the handle and the end of the plank and tried to hold ontothe handle, we would slide off the end of the plank when the rotation of the plank reached a certain speed. Therefore, we learned to sit with our legs across thehandle, with the handle pressing against the back insides of our knees. By doing this, we could survive without sliding off the plank no matter how fast the third child caused theplank to rotate.

Why am I telling you this?

Although I didn't understand it at the time, when the plank was rotating around its spindle at a relatively high rate of speed, the handle exerted a force on the inside of both knees. Inother words, the handle exerted a force on each leg in the direction of the center of the plank. This is a force that we will call a centripetal force .

Centripetal force

According to The Physics Classroom , any object moving in a circle (or along a circular path) experiences a centripetal force. That is, there is some physical forcepushing or pulling the object towards the center of the circle. This is the centripetal force requirement.

The word centripetal is merely an adjective used to describe the direction of the force. We are not introducing a newtype of force but rather describing the direction of the net force acting upon the object that moves in the circle. Whatever the object, if it movesin a circle, there is some force acting upon it to cause it to deviate from its straight-line path, accelerate inwards and move along a circular path.

A centripetal force on my body

The effect of this centripetal force was to cause my body to accelerate in the direction of the force, which was directly toward the spindle at the center of the plank.The spindle was at the center of the circle around which I was experiencing circular motion (although probably not uniform circular motion).

A weight on a string

Consider tying a weight, such as a full bottle of soda, to the end of a string. Then swing the bottle around and around above your head in anapproximate circle. You will feel a force pulling your hand toward the periphery of the circle, so you will exert a force on the string to keep the bottle fromflying away. The force that you exert on the string will be exerted on the bottle at the other end of the string and that force will be directed along thestring towards the center of the circle. That is the force that we will refer to as centripetal (center seeking) force, and that force will act on the mass ofthe bottle to cause the bottle to accelerate in the direction of the center of the circle.

What happens if the string breaks?

If the string breaks, there will no longer be a centripetal force acting on the bottle and it will fly off into space along a line that is tangential to itslocation on the circle at the instant the string breaks. It won't continue moving in a circle. Instead, it will move in a straight line until the resistance ofthe air and force of gravity bring it to a sudden stop on the ground. (Actually, it will move along a parabolic arc under the force of gravity until it strikesthe ground.)

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Accessible physics concepts for blind students. OpenStax CNX. Oct 02, 2015 Download for free at https://legacy.cnx.org/content/col11294/1.36
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