8. A solid homogeneous sphere is moving on a rough horizontal surface, partly rolling and partly sliding During this kind of motion of the sphere:
(a) total kinetic energy is conserved
(b angular momentum of the sphere about the point of contact with the plane is conserved (c) only the rotational kinetic energy about centre of mass is conserved
(d) angular momentum about centre of mass is conserved
8. A solid homogeneous sphere is moving on a rough horizontal surface, partly rolling and partly sliding During this kind of motion of the sphere:
(a) total kinetic energy is conserved
(b angular momentum of the sphere about the point of contact with the plane is conserved (c) only the rotational kinetic energy about centre of mass is conserved
(d) angular momentum about centre of mass is conserved
At the point of contact the frictional force acts tangentially and the weight of the sphere passes through it perpendicularly and there is no other force acting on the sphere. So, as all forces pass through the point of contact, the moment of all forces acting in the body about the point of contact is zero.Hence there is no torque about the point of contact which means angular momentum about the point of contact must be conserved.
At the point of contact the frictional force acts tangentially and the weight of the sphere passes through it perpendicularly and there is no other force acting on the sphere. So, as all forces pass through the point of contact, the moment of all forces acting in the body about the point of contact is zero.Hence there is no torque about the point of contact which means angular momentum about the point of contact must be conserved.
