Question

please give the correct ans it will much help me​

Answer 1

Answer:

Let vcm is the velocity of the centre of mass of a disc-shaped body. Since for a rolling disc, the centre of mass would lie at the geometric centre C, the velocity of body or velocity of C is vcm which is parallel to the rolling surface. The rotational motion of the body occurs about its axis of symmetry, therefore, the velocity at any point P0, P1 or P2 of the body comprises two parts, translational velocity vcm and due to rotational motion, it has linear velocity vr, where vr = rω. ω is the angular velocity of the rolling disc. vr is perpendicular to radius vector at any point lying on the disc with respect to the geometric centre C. Consider the point P0 on the disc. vr is directed opposite to vcm and at this point vr = R ω , where R is the radius of the disc. Therefore, for the disc, the condition for rolling without slipping is given by vcm = R ω.

The kinetic energy of such a rolling body is given by the sum of kinetic energies of translational motion and rotation.

Answer 2

Answer:

"Force required by engine = (94000x9.81) sin30

Power output by engine = Fv = [(94000x9.81) sin30] x 6.0 = 2766420W

Efficiency = Power output / Power input = 40% = 0.4

Power input = 2766420 / 0.40 = 6.9MW "