Vriti Edustoregreat concepts about rolling motion
15 Dec 2008 20:44:44 IST
great concepts about rolling motion
Engineering Entrance
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JEE Main
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JEE Advanced
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Physics
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Mechanics
Rolling Motion or Combined rotation and translation
DEFINITION:
A body which is not only rotating but also translating is said to make rolling motion.
- The displacements of all points in the body are different (generally except when it has made complete revoultions).
- The centre of mass always has a translational motion (no rotational motion).
- This is valid if the axis of rotation is the centre of mass as otherwise there will be a pseudo torque that we would have to consider.
TYPES:
Rolling motion can be of three types:
- Pure rolling or rolling without slipping: In this case distance travelled by the centre of mass is equal to 2
R. - Rolling with forward slipping: in this case the distance travelled by the centre of mass is more than 2
R. - Rolling with backward slipping: in this case the distance travelled by the centre of mass is less than 2R.
KINEMATICS:
- Displacement, velocity and acceleration of any point P on the body can be calculated by:
s = scm + sp,cm where all terms are vector quantities
v=vcm + vp,cm
a = acm + ap,cm
General Misconceptions:
- V=R
is not the defining equation of pure rolling. This is only valid if the surface on which the body is rolling is stationary. - If the surface is not stationary, then defining equation is acceleration of point of contact with respect to the moving surface is zero.
- Friction is necessary for rollling motion. This is not true. When a body is already in pure rolling there is no frictional force acting on the body. Similarly, if a force is applied tangentially on the top of a ring then no friction is necessary to continue pure rolling.
- In rolling motion, friction acts in a direction so as to ensure that acceleration of point of contact is zero regardless of whether it promotes or slows down motion.
- Work done by friction in pure rolling is zero as the point of contact remains at rest relative to the surface hence the displacement of the point of contact is zero.
Comments (12)
abhinav
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Joined: 16 Nov 2008 21:35:25 IST
Posts: 172
15 Dec 2008 21:46:45 IST
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THANX MAN U GAVE A GOOD ARTICLE ..................
5 Jan 2009 23:27:33 IST
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SUGGESTION-------------YOUR MISCONCEPTION SECTION IS A BIT CONFUSING -------------SHOULD HAVE GIVEN THE HEADING "IMPORTANT CONCEPTS".........BECAUSE PEOPLE WILL THINK THAT THE STATEMENTS GIVEN THERE ARE MISCONCEPTIONS!!!!!!!
28 Jan 2009 18:58:24 IST
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CAN U GO IN DEPTH OR SUGGEST AN ARTICLE OR SITE IF U KNOWTO EXPLAIN HOW ACTUALLY FRICTION COMES TO PLAY?SOME EXPERTS FEEL ITS NOT DUE TO INTERLOCKING OF 2 SURFACES IN CONTACT!!
24 Aug 2009 09:27:57 IST
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thx ... it helped me clear doubts of this chapter and i can do irodov sums of this chapter now... :-)
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