<< Chapter < Page Chapter >> Page >

Therefore, if an object is moving in a horizontal circle at constant speed, the centripetal force does no work on the object and cannot change the totalmechanical energy of the object. The kinetic energy will remain constant and therefore, the speed of the object will remain constant. The centripetal forcewill accelerate the object by changing its direction but will not change its speed.

Centripetal, not centrifugal

Don't confuse centripetal force with the word centrifugal . For some reason, many people mistakenly use the word centrifugal (meaning outward) whenthey should use the word centripetal. In this case, centripetal is the correct word.

Maybe this is like the use of the words nuclear and nucular. Which is correct? I will leave that as an exercise for the student to determine.

Summary

An object in uniform circular motion must experience an unbalanced force pointing towards the center of the circle. This force is referred to as a centripetal force, where centripetalmeans inward seeking .

This force is required to cause the object to continually change its direction in order to move along a circular path without changing its speed.

Because the centripetal force is directed perpendicular to the tangential velocity vector, the centripetal force cannot change the total mechanical energy possessedby the object (the cosine of 90 degrees is 0).

Because the centripetal force has no impact on the potential energy possessed by the object, and because it cannotchange the total mechanical energy, it cannot change the kinetic energy possessed by the object. Since it can't change the kinetic energy, it can'tchange the object's speed.

However, it can change the object's direction without changing its speed.

Example Scenarios

Scenario #1

An object is moving with uniform circular motion in a counter-clockwise direction around a circle whose center is at the origin in a Cartesian coordinate system. When the object passesthrough the intersection of the circle with the positive horizontal axis, what is the direction of the velocity vector relative to the horizontal axis?

  1. 0 degrees
  2. 180 degrees
  3. 90 degrees
  4. 270 degrees
  5. 30 degrees

The correct answer is #3, 90 degrees. At that point, the line tangent to the circle touches the circle where it intersects the positive horizontal axis andis perpendicular to the horizontal axis. Because the motion is counter-clockwise, the vector points up at 90 degrees (instead of down at 270degrees) relative to the positive horizontal axis.

Scenario #2

An object is moving with uniform circular motion in a counter-clockwise direction around a circle whose center is at the origin in a Cartesian coordinate system. When the object passesthrough the intersection of the circle with the positive horizontal axis, whatis the direction of the acceleration vector relative to the positive horizontal axis?

  1. 0 degrees
  2. 180 degrees
  3. 90 degrees
  4. 270 degrees
  5. 30 degrees

The correct answer is #2, 180 degrees. The acceleration vector for an object under uniform circular motion always points in the direction of the center ofthe circle. At the intersection of the circle with the positive horizontal axis, the direction of the center of the circle is 180 degrees relative to thepositive horizontal axis.

Scenario #3

A heavy object is being swung on a string in a counter-clockwise direction around a circle whose center is at the origin in a Cartesian coordinate system. The plane of thecircle is parallel to the ground so that we can ignore the effects of gravity.

Just as the object passes through the intersection of the circle with the positive horizontal axis, thestring breaks allowing the object to fly off into the nearby playground space. What is the direction of motion of the object relative to the positivehorizontal axis?

  1. 0 degrees
  2. 180 degrees
  3. 90 degrees
  4. 270 degrees
  5. 30 degrees
  6. The object will continue to move in a circle.

The correct answer is #3, 90 degrees, which is the direction of the velocity vector at the instant that the string breaks. Because there will no longer be acentripetal force to cause the object to change direction and stay on the circular path, it will continue moving in the direction that it is moving whenthe string breaks.

Resources

I will publish a module containing consolidated links to resources on my Connexions web page and will update and add to the list as additional modulesin this collection are published.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Circular Motion -- Acceleration and Centripetal Force
  • File: Phy1250.htm
  • Revised: 10/02/15
  • Keywords:
    • physics
    • accessible
    • accessibility
    • blind
    • graph board
    • protractor
    • screen reader
    • refreshable Braille display
    • JavaScript
    • trigonometry
    • uniform circular motion
    • tangential
    • velocity vector
    • centripetal force
    • work-energy
Disclaimers:

Financial : Although the openstax CNX site makes it possible for you to download a PDF file for the collection that contains thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

You also need to know that Prof. Baldwin receives no financial compensation from openstax CNX even if you purchase the PDF version of the collection.

In the past, unknown individuals have copied Prof. Baldwin's modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing Prof. Baldwin as the author.Prof. Baldwin neither receives compensation for those sales nor does he know who doesreceive compensation. If you purchase such a book, please be aware that it is a copy of a collection that is freelyavailable on openstax CNX and that it was made and published without the prior knowledge of Prof. Baldwin.

Affiliation : Prof. Baldwin is a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how to synthesize TiO2 nanoparticles by chemical methods
Zubear
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Accessible physics concepts for blind students' conversation and receive update notifications?

Ask