Centripetal Force (1 Viewer)

[gn02622015]

Can any one tells me why the object is accelerating towards the centre in circular motion ?

 

[idling fire]

A very quick explanation of why centripetal acceleration is towards the centre is to look at the vector diagram. Draw a circle, and mark two points on the circumference (deciding one to be initial and one to be final). Draw the velocity vectors at these two points (as tangents to the circle at those points and preferably of equal length).

Now a = change in velocity / change in time.
So when you look at it as a vector diagram, the change in velocity is v-u. When this is done, you can see that it points towards the centre of your circle. And... yeah...

Hope this was useful... :/

 

[twilight1412]

actually erday 8:30 PM idling fire although i hate to correct you after your great explanation you are wrong in one respect

only the instantaneous acceleration points towards the center so the closer the points are it will approach the center but will only point to the center if its instantaneous ><

btw the actual force if you think about it is friction ^^
if there are no other forces involved eg hailstorms avalanches then the centripetal force is friction

 

[idling fire]

Oh yeah, I see what you mean... whoops

That "one respect" was pretty much the only respect that mattered, so entirely incorrect. Don't listen to me, I'm a n00b.

 

[gn02622015]

Is there an answer to my question ?

 

[angmor]

ill put it simply to you.

acceleration is simply a change in velocity.
now, velocity is a vector quantity. that is, if it changes direction, then velocity also changes.
therefore the way the ball spins in a circle is a change in velocity/change in direction, thus it is accelerating.

 

[airie]

Can any one tells me why the object is accelerating towards the centre in circular motion ?

Centripetal force is supplied by and only by the gravitational field of the central body, thus an object under the effect of centripetal force will accelerate towards this central body.

 

[gn02622015]

I know the theory of centripetal force . What i need is a detail explantion of why the centripedal acceleration is pointing towards the centre of circle.

 

[mitsui]

think in this way:

try throw something around in a circle attached to a string..

the only force exists is centripetal force
the only thing that is supplying it is your hand
the only direction the object is feeling a pull is towards the hand.

hope that helps

forces and velocities are totally different and seperated concepts. =)

 

[airie]

Yeah, because the only force acting on the object is the centripetal force, which is solely supplied by the gravitational field of the central body (which accelerates things towards this body, as it is ITS field), so the object will be accelerated towards the centre.

 

[rama_v]

Yeah, because the only force acting on the object is the centripetal force, which is solely supplied by the gravitational field of the central body (which accelerates things towards this body, as it is ITS field), so the object will be accelerated towards the centre.

http://www.physclips.unsw.edu.au/

Look at the bit on circular motion.

In answer to your question, you need to understand a bit of calculus to realise why instantenous acceleration is directed towards the centre. Acceleration is defined as the derivative of velocity with respect to time. If you take the velocity v of some mass moving in circular motion at any one time, lets call it t, and then take the velocity of the same mass at some time t + Δt, you you can see that the velocity has changed (as the direction has changed). We can represent this by drawing vectors. The change in velocity can be drawn as a vector Δv. When Δt is quite small you can see that the change in velocity is almost perpendicular to the initial velocity. So as Δt -> 0, then the angle -> 90 degrees. This is why the centripetal acceleration is directed towards the centre - it can be explained in terms of simply geometry.

Also, in a string/mass system the centripetal force is provided entirely by the tension force of the string assuming uniform circular motion. The acceleration of the object is independent of its mass -> a = v²/r