Question

Underline the correct alternative :

(a) When a conservative force does positive work on a body, the potential energy of
the body increases/decreases/remains unaltered.
(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 is the total kinetic energy/total linear momentum/total energy of
the system of two bodies

Answer 1

Explanation:

a. Decreases

When a body is displaced in the direction of the force, positive work is done on the body by the conservative force due to which the body moves to the centre of force. Thus the separation between the two decreases and the potential energy of the body decreases.

b.Kinetic energy

The velocity of the body is reduced when the work done is in the direction opposite to that of friction. Thus, the kinetic energy decreases

c. External force

Change in momentum cannot be produced by internal forces, irrespective of their directions. Thus, the change in total momentum is proportional to the external force on the system.

d.Total linear momentum

Irrespective of elastic collision or an inelastic collision, the total linear momentum remains the same.