Is Centripetal Acceleration Constant in Uniform Circular Motion?

Click For Summary
In uniform circular motion, centripetal acceleration is constant and directed towards the center of the circular path, maintaining the object's circular trajectory. This acceleration changes the direction of the object's velocity but not its magnitude, meaning the speed remains constant. The centripetal force, which is necessary for this motion, is provided by an external force, such as tension in a string or gravitational force. While the object's speed is constant, the acceleration is responsible for the continuous change in direction, not for changing the speed itself. Understanding these concepts clarifies the relationship between speed, velocity, and the forces acting on an object in circular motion.
faiziqb12
Gold Member
Messages
105
Reaction score
3

Homework Statement


i was going through uniform circular but a confusion popped out of my head .
as i have read before the Rutherford atomic model was only rejected due to
the fact that electrons moving in circular orbits need to accelerate constantly
to maintain a uniform speed but the acceleration causes electrons to radiate
the energy and they would eventually lose all their energy and fall into the
nucleus ... so my question is in uniform circular motion there is a constant
acceleration which keeps a uniform speed..is it centripretal acceleration?
how?... and how to calculate the magnitude and direction of this
acceleration? ... and is it a constant?
 
Physics news on Phys.org
What are your answers?
 
tms said:
What are your answers?
i am empty
i was trying to add up the the gravitation,friction and centripretal acceleration vector
but it proved of no use
 
i have ran out of my mind
and here are no websites that can help me
please help!
 
faiziqb12 said:
so my question is in uniform circular motion there is a constant
acceleration which keeps a uniform speed..is it centripretal acceleration?
how?... and how to calculate the magnitude and direction of this
acceleration? ... and is it a constant?
What is centripetal acceleration ? What causes it ?
 
Qwertywerty said:
What is centripetal acceleration ? What causes it ?
NO MY QUESTION ACTUALL IS THE SAME AS I HAVE POSTED
the centripetal force just allows a body to be fixed in a circular orbit but what causes the object to keep a fixed velocity in that circular orbit
 
faiziqb12 said:
the centripetal force just allows a body to be fixed in a circular orbit but what causes the object to keep a fixed velocity in that circular orbit
Is the velocity constant ? Does uniform circular motion maintain constant speed , or constant velocity ?
 
Qwertywerty said:
Is the velocity constant ? Does uniform circular motion maintain constant speed , or constant velocity ?
oh sorry constant speed
 
Okay , so it is now clear that velocity of the object is changing .

Now , for constant mass systems , if velocity of object is changing , then what does that say about object's acceleration - is it zero ?
 
  • #10
Qwertywerty said:
Okay , so it is now clear that velocity of the object is changing .

Now , for constant mass systems , if velocity of object is changing , then what does that say about object's acceleration - is it zero ?
yes
 
  • #11
faiziqb12 said:
yes
No , it isn't !

What causes change in velocity ?
 
  • #12
Qwertywerty said:
No , it isn't !

What causes change in velocity ?
i was talking about magnitude...
now you come on the question
i can see two types of acceleration
one that keeps the object the object in orbit{centripedal acceleration}

my question is about the second one ..that one which keeps a uniform speed or say a uniform magnitude of velocity
 
  • #13
Qwertywerty said:
No , it isn't !
you are right
 
  • #14
faiziqb12 said:
one that keeps the object the object in orbit{centripedal acceleration}

my question is about the second one ..that one which keeps a uniform speed or say a uniform magnitude of velocity
Consider a pebble tied to a string , rotated about a fixed point . As it starts to spin , tension acts as a centripetal force , consequently causing an acceleration - which is the centripetal acceleration .

This acceleration is responsible for circular motion . For uniform circular motion , this is the pebble's only acceleration .
It causes change in velocity of the pebble . As this is perpendicular to initial velocity of pebble , it only causes a change in the pebble's direction of motion of the pebble , working like this throughout the circular motion .

Thus , my question to you is this - how is the acceleration changing the velocity ( we have already seen that velocity is changing ) ?
Also , how is velocity ( a vector ) related to speed ( a scalar ) ?
 
  • #15
Qwertywerty said:
This acceleration is responsible for circular motion. For uniform circular motion , this is the pebble's only acceleration .
Also , how is velocity ( a vector ) related to speed ( a scalar ) ?
THE centripetal force is only responsible for keeping the body in orbit not for increasing,decreasing or maintaining its speed.
in uniform circular motion there is constant speed due to the force applied by us repeatedly...and this force is the second type of acceleration
now my question is how can i calulate the amount of such acceleration needed to maintain uniformity of speed
i hope you would have understood my question now
 
  • #16
Please understand , I have got your question . What my problem is that you seem to be making mistakes in your basic concepts .

So please answer these -
Qwertywerty said:
Thus , my question to you is this - how is the acceleration changing the velocity ( we have already seen that velocity is changing ) ?
Also , how is velocity ( a vector ) related to speed ( a scalar ) ?
 
  • #17
Qwertywerty said:
Please understand , I have got your question . What my problem is that you seem to be making mistakes in your basic concepts .

So please answer these -
velocity has direction along with magnitude so it is a vector and speed has only a magnitude so it is a scalar
also acceleration is changing the velocity by changing its direction
 
  • #18
faiziqb12 said:
velocity has direction along with magnitude so it is a vector and speed has only a magnitude so it is a scalar
also acceleration is changing the velocity by changing its direction
So , in the entire motion , only direction of the velocity is changing , and not it's magnitude . So if it's magnitude isn't changing , speed isn't changing .

So , to finally answer your question , no acceleration is causing uniform speed . Speed was never changing , and hence no acceleration was ever required to do so .
 
  • #19
Qwertywerty said:
So , in the entire motion , only direction of the velocity is changing , and not it's magnitude . So if it's magnitude isn't changing , speed isn't changing .

So , to finally answer your question , no acceleration is causing uniform speed . Speed was never changing , and hence no acceleration was ever required to do so .
what you want to say is if we stop rotating the string in the example , but not let the string go.then the ball will again be in uniform motion.

no, it wont

we revolve our hands to give the desired force always to cancel the effect of gravitational force and the frictional force in the example given

and this force is actually the another accleration i was talking about
 
  • #20
faiziqb12 said:
what you want to say is if we stop rotating the string in the example , but not let the string go.then the ball will again be in uniform motion.
?

How exactly would you do this ?
 
  • #21
faiziqb12 said:
we revolve our hands to give the desired force always to cancel the effect of gravitational force and the frictional force in the example given
Again , what example ? What force of the hand ?
 
  • #22
the example is that a string is attached to a ball on one side and a figer on the other side
we rotate the finger that's the force of the hand
 
  • #23
According to Newton's first law of motion, it is the natural tendency of all moving objects to continue in motion in the same direction that they are moving ... unless some form of unbalanced force acts upon the object to deviate its motion from its straight-line path. Moving objects will tend to naturally travel in straight lines; an unbalanced force is only required to cause it to turn. Thus, the presence of an unbalanced force is required for objects to move in circles.
this unbalanced force is the force of the hand
 
  • #24
faiziqb12 said:
According to Newton's first law of motion, it is the natural tendency of all moving objects to continue in motion in the same direction that they are moving ... unless some form of unbalanced force acts upon the object to deviate its motion from its straight-line path.
This is the centripetal force , provided by the string . Please reread the previous posts .
 
  • #25
Edit : Do you feel your question has been answered already ?
 
Last edited:
  • #26
N
Qwertywerty said:
You seem to be stating facts ( facts - accodin to you ) . Has your question thus been answered already ?
O IT IS A QUESTION
MY QUESTION IS THAT HOW TO CALCULATE THE SECOND TYPE OF ACCELERATION BESIDES CENTRIPETAL WHICH I MENTIONED EARLIER
 
  • #27
faiziqb12 said:
MY QUESTION IS THAT HOW TO CALCULATE THE SECOND TYPE OF ACCELERATION BESIDES CENTRIPETAL WHICH I MENTIONED EARLIER
There is no other acceleration of the rotating object .
 
  • #28
i said earlier that there is and also explained it
 
  • #29
faiziqb12 said:
i said earlier that there is and also explained it
Edit : If an object's velocity is changing in the sense that it's direction changes but not it's magnitude , then force is not affecting the speed of the object - because magnitude of velocity isn't changing in that case , only it's direction is .
 
Last edited:
  • #30
Qwertywerty said:
If an object moves with a constant speed , there cannot be an acceleration of the body .
You mean a constant velocity.
 
  • #31
tms said:
You mean a constant velocity.
No , sorry , that's not what I meant . See my edited post .
 
  • #32
Qwertywerty said:
Edit : If an object's velocity is changing in the sense that it's direction changes but not it's magnitude , then force is not affecting the speed of the object - because magnitude of velocity isn't changing in that case , only it's direction is .
yes that's true but in places like planetary motion
here in the string example there is gravitation of Earth and to balance it u need a constantly applied force
thats what i am talking about
 
  • #33
Suppose the object is kept on a table . Then , in that case , normal cancels gravitational force .
If it is a vertical circular motion , analysis is not so simple .
faiziqb12 said:
here in the string example there is gravitation of Earth and to balance it u need a constantly applied force
thats what i am talking about
I'm sorry , is this what you have been talking about this whole time ?
 
  • #34
maybe u still don't understand my question
 
  • #35
Okay , could you please repeat your question ? Also state exactly what kind of circular motion the object is doing .
 
  • #36
my question is
a body is in a uniform circular motion on Earth
it means that we balanced all the unbalanced forces acting on it to create a uniform velocity
so how much is the force we applied to balance the forces?
 
  • #38
On the surface , or in the air ? You mean , uniform speed ?
Also , it's to a string and the only other force is the force of gravity ?
 
  • #39
Qwertywerty said:
On the surface , or in the air ? You mean , uniform speed ?
Also , it's to a string and the only other force is the force of gravity ?

its in the air
and you i meant uniform speed
i never said there's only these two forces

leave it i understood all of it
now i just need this part of the question be answered
https://www.physicsforums.com/threads/the-beggining-of-everything.826753/
 

Similar threads

Acceleration in uniform circular motion is uniform or non-uniform?
2
Replies
55
Views
3K
Relation between the velocity vector and the acceleration vector of an object
Replies
1
Views
723
Vertical circular motion
Replies
8
Views
2K
A Car on a Banked Curve Moving in Uniform Circular Motion
Replies
7
Views
3K
Find the acceleration in circular motion
Replies
6
Views
2K
What actually is the centripetal acceleration formula?
Replies
28
Views
3K
Is Vertical Circular Motion Ever Uniform?
Replies
10
Views
3K
Difference between radial and centripetal acceleration?
Replies
9
Views
8K
Acceleration in non-uniform circular motion
Replies
1
Views
2K
Kinematics: Acceleration of a figure skater changing direction
Replies
16
Views
1K