Physics 1st Year Chapter 5 Notes

• Important from physics 1st year chapter 5 numericals Punjab Textbook.
• Angular displacement
• angular velocity: Very often we are interested in knowing how fast or how slow a body is rotating. It is determined by its angular velocity which is defined as the rate at which the angular displacement is changing with time. Referring to Fig. 5.1(c). if af is the angular displacement during the time interval Al, the average angular velocity during this Interval is given by The instantaneous angular velocity is the limit of the ratio AB/Af as At. following instant f, approaches to zero. Thus In the limit when of approaches zero, the angular displacement would be infinitesimally small, So it would be a vector quantity and the angular velocity as defined by  Eq.5.3 would also be a vector. Its direction is along the axis of rotation and is given by right hand rule as described earlier.
• Angular velocity is measured in radians per second which is Its Si unit. Sometimes it is also given in terms of revolution per minute.
• angular acceleration: When we switch on an electric fan, we notice that its angular velocity goes on increasing. We say that it has an angular acceleration. We define angular acceleration as the rate of change of angular velocity, If, and are the values of instantaneous velocity of a rotating body at Instants & and, the average angular acceleration during the interval - is given by M. The instantaneous angular acceleration is the limit of the ratio as Af approaches zero. Therefore, instantaneous At angular acceleration is given by relation between angular and linear velocities.
• The angular acceleration is also a vector quantity whose magnitude is given by Eq. 5.5 and whose direction is along the axis of rotation. Angular acceleration is expressed in units of rads. Till now we have been considering the motion of a particle P on a circular path. The point P was fixed at the end of a rotating massless rigid rod. Now we consider the rotation of a rigid body as shown in Fig. 5.3. Imagine a point P on the rigid body. Line OP is the perpendicular dropped from Pon the axis of rotation. It is usually referred as referencв line. As the body rotates, line OP also rotates with it with the same angular velocity and angular acceleration. Thus the rotation of a rigid body can be described by the rotation of the reference line OP and all the terms that we defined with the help of rotating line OP are also valid for the rotational motion of a rigid body. In future while dealing with rotation of rigid body, we will replace by it reference line OP.
• RELATION BETWEEN ANGULAR AND LINEAR VELOCITIES: Consider a rigid body rotating about z-axis with an angular velocity as shown in Fig. 5.4 (a). Imagine a point P in the rigid body at a perpendicular distance r from the axis of rotation. OP represents the reference line of the rigid body. As the body rotates, the point P moves along a circle of radius with a linear velocity v whereas the line OP rotates with angular velocity as shown in Fig. 5.4 (b). We are interested in finding out the relation between and v. As the axis of rotation is fixed, so the direction of always remains the same and can be manipulated as a scalar. As regards the linear velocity of the point P, we consider its magnitude only which can also be treated as a scalar. Suppose during the course of its motion, the point P moves through a distance P.P. = \s in a time interval af during which reference line OP has an angular displacement 10 radian during this interval, sa and 10 are related by Eq. 5.1.
• Equations of angular motion
• centripetal force
• moment of inertia
• angular momentum
• law of conservation of angular momentum
• rotational kinetic energy
• the rotational kinetic energy of a disc and hope
• artificial satellites
• Real and Apparent weight
• weightlessness in satellite and gravity-free system
• orbital velocity
• artificial gravity
• geostationary orbits
• communication satellite 
• Newton's is Einstein's views of gravitation

Total Page = 73 pages

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