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PART - 1 CH - 5Work, Energy and Power — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysicsPART - 1 CH - 5Work, Energy and Power3 Marks
Question
Underline the correct alternative :
(a) When a conservative force does positive owrk 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 are the total kinetic energy/total linear momentum/total energy of the system of two bodies
✓

Answer

(a) When a conservative force does positive work on an object, the potential energy of the object decreases.
Since the conserved force does positive work on an object when it displaces the object in the direction of the force. Due to this, the object moves towards the center of force and thus reduces the value of x. That is why its potential energy decreases.
(b) Work done by an object against friction always result in a loss in its kinetic energy. The main reason for this is that the work done against friction reduces the kinetic energy of the object.
(c) The total momentum of a system can't be converted into internal force, hence the rate of change of total
momentum in a system consisting of many particles is proportional to the external force applied on the system.
(d) In an inelastic collision of any two bodies, the quantities which don't change after the collision are the total linear momentum of the system and its total energy (if the system is isolated). The total kinetic energy (KE)
of the system is not conserved because it converted into some other form of energy in equal amount.

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