ICNS 132 : Circular MotionRotational Motion

Weerachai Siripunvaraporn

Department of Physics, Faculty of ScienceMahidol Universityemail&msn : wsiripun2004@hotmail.com

even though an object moves at a constant speed in a circular path, it still has an acceleration.

Rotational Motion & Circular Motion & SHM

Rotational Motion

(Rigid Object)

SHM Motion

Polar Coordinate

P is rotated counter-clockwise.

We choose a reference line on the object, such as a line connecting O and a chosen particle on the object.

The angular position of the rigid object is the angle between this reference line on the object and the fixed reference line in space, which is often chosen as the x axis.

This is similar to the way we identify the position of an object in translational motion—the distance x between the object and the reference position, which is the origin, x = 0.

final angular position f

Initial angular position i

The angular velocity of an object describes how fast it is turning about an axis in the time interval t, and is defined as follows:

Angular velocity (ω)

Tangential velocity (v)

although every point on the rigid object has the same angular speed, not every point has the same tangential speed because r is not the same for all points on the object.

tangential acceleration of the point P

tangential acceleration of the point P

centripetal acceleration at that point