question_answer 6)

Underline the correct alternative: (a) When a conservative force does positive work on a body, the potential energy of the body increases I 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 are the total kinetic energy/total linear momentum/total energy of the astern of two bodies.  

Answer:

(a) The work done by a conservative force is equal to the negative of the potential energy. Wizen the work done is positive, the potential energy decreases. (b) Friction always opposes motion. A body does work against friction at the expense of its kinetic energy. Work done by a body against friction results in a loss of its kinetic energy. (c) Internal forces in a many-particle system cancel out in pairs and so they cannot change the net momentum of the system. Only the external forces can produce change in momentum. The rate of change of momentum of a many-particle system is proportional to the external force on the system. (d) In an elastic collision, the kinetic energy of the system decreases after the collision but the total energy of the system and its total linear momentum do not change after the inelastic collision?