(b) Work done by a body against friction always results in a loss of its kinetic / potential energy.
(c) The rate of change of total momentum of a many-particle system is proportional to the external force / sum of the internal forces on the system.
(d) In an inelastic collision of two bodies, the quantities which do not change after the collision are the total kinetic energy / total linear momentum / total energy of the system of two bodies.(b)
The work
done against the direction of friction reduces the velocity of a body. Hence,
there is a loss of kinetic energy of the body.
Work
Energy Principle
W=changeinKE
since
Work done by Friction is negative, it results in decrease of KE
(c)
Internal
forces, irrespective of their direction, cannot produce any change in the total
momentum of a body. Hence, the total momentum of a many- particle system is
proportional to the external forces acting on the system.
since
there is no external force acting
Fext=dPdt