11th Class Physics Systems Of Particles & Rotational Motion / कणों के निकाय तथा घूर्णी गति

  • question_answer 27)
    Prove the result that the velocity  of translation of a rolling body (like a ring, disc, cylinder or sphere) at the bottom of an inclined plane of a height h is given by                 using dynamical consideration (i.e., by consideration of forces and torques). Note k is the radius of gyration of the body about its symmetry axis, and R is the radius of the body. The body starts from rest at the top of the plane.  

    Answer:

    Velocity attained by a body rolling down an inclined plane. Consider a body of mass M and radius R rolling down a plane inclined at an angle  with the horizontal, as shown in Fig. 7.107. It is only due to friction at the line of contact that body can roll without slipping. The centre of mass of the body moves in a straight line parallel to the inclined plane. The external forces on the body are (i) The weight Mg acting vertically downwards. (ii) The normal reaction N of the inclined plane. (iii) The force of friction acting up the inclined plane.     Fig. 7.107 Fig, 7.107 A body rolling without slipping on an inclined plane. Let a be the downward acceleration of the body. The equations of motion for the body can be written as     As the force of friction  provides the necessary torque for rolling, so   or              where k is the radius of gyration of the body about its axis of rotation. Clearly   or              Let h be height of the inclined plane and s the distance travelled by the body down the plane. The velocity  attained by the body at the bottom of the inclined plane can be obtained as follows:   or              or                             


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