which are the important tricks to solve problems in rotational dynamics? give me some examples.

Dear student,

We will now have a look at some of the terms used in rotational dynamics:

Angular velocity is an important quantity.  Suppose we had a record deck turntable turning at 33 rpm (revolutions per minute).  Clearly an object at the rim of the turntable moves with a higher linear speed that an object towards the centre.  However both move through the same angle every second.  We call this the angular velocity, which has the physics code w.  We don't use degrees per second, but radians per second.  Go back to Module 4 if you are not sure what a radian is. (1 rad » 57^o)  Radians are dimensionless units, so are ignored in unit analysis.  Some purists say they should be left out altogether.  In these notes I will always include them.

Every revolution, all parts of the object turn through 2p radians.

A common way of expressing the rate of turning is revolutions per minute.  All the equations we will use need the rate of turning (angular velocity) to be in radians per second.  Therefore be a good chap and convert the revolutions per minute to radians per second.

Angular velocity = 2p(rpm ÷ 60)

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All the best.

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Sagar Singh

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Draw a neat diagram of the system.Calculate the moment of Inertia of the system about the rotational axisFirstly consider the origin of the forces acting on the each object.To do this find out the field forces acting on the each object.Wherever contact in available account the contact force carefullyFind out the torque for each of the forcesFind out the angular accelerationLaw of conservation of angular momentum helps in many cases which states if no torque ,angular momentum remains conserved