Tiêu đề ROTATION OF RIGID BODY.pdf ✅

0 PHYSICS FORM FIVE ROTATION OF RIGID BODY MsomiBora.com The Best Education Blog in Tanzania
1 ROTATION OF RIGID BODY Rigid body ideally a rigid body is a body with a perfectly definite and unchanging shape. The distances between different pairs of such a body do not change on the application of force. Pure Translation or Translation • A body is said to have pure translational motion, if each particle of it has same velocity/acceleration at a particular instant of time. Rotational Kinematics • Kinematics is the study of motion without reference to the forces which cause motion. • Kinetics is the study of motion which relates the action of forces on bodies to their resulting motions. • Kinematics and Kinetics together known as Dynamics. • As earlier we have studied about displacement (r), velocity (v) and acceleration (a) in the chapter kinematics; in the same way we shall study here about angular displacement (θ), angular velocity (ω) and angular acceleration (α) . Angular Displacement • Let us consider an arbitrary shaped rigid body rotating in counter-clockwise direction about an axis passing through point O. Here axis of rotation AB is passing through point O and is perpendicular to the plane of rotation.
2 • Let us consider a particle on the body at a distance r from the axis of rotation. Clearly, this particle is moving along a circle of radius r. Suppose at a time t, this particle was at point P and after a time t + Δt it is at point P’. • Clearly, during this time interval, particle P rotates through an angle θ from initial line OP. This angle θ is known as angular displacement of the particle. • The line OP is known as reference position. • It is clear that all the particle of the body has rotated through the same angle θ. Therefore, we can say that the whole rigid body has rotated through an angle θ. Hence, we can say that the rigid body has an angular displacement θ. IMPORTANT POINTS ABOUT ANGULAR DISPLACEMENT • Angular displacement is a scalar quantity. Infinitesimal small angular displacements are vectors. • Denoted by Δθ or θ • S.I. unit: radian (rad) 1800 = π rad Angular Velocity (Ω) • Average angular velocity (Δω): It is defined as the time rate of change of angular displacement over a time interval.