Embibe Experts Solutions for Chapter: Work, Energy and Power, Exercise 8: Exercise (Assertion & Reason)

Assertion: Frictional forces are conservative forces.

Reason: Potential energy can be associated with frictional forces.

Assertion: The change in kinetic energy of a particle is equal to the work done on it by the net force. 
Reason: Change in kinetic energy of the particle is equal to the work done only in the case of a system of one particle.

Assertion: When a force of $20 \mathrm{N}$ displaces a body by $5 \mathrm{m}$, then work done by this force must be $100 \mathrm{J}$ for every observer watching that body.

Reason: Work done on a body does not depend on the observer that is observing the body.

Assertion: When spring is elongated work done by spring is negative but when it is compressed work done by spring is positive.

Reason: Work done by spring is path-dependent.

Assertion: Work done by force of friction in moving a body in any round trip is zero.

Reason: Frictional force is a conservative force.

Assertion : A particle moving one dimensionally in conservative field may have more than one turning points.  
Reason : Turning point depends on initial velocity.

Assertion : For an isolated system, mechanical energy is not conserved. 
Reason : For an isolated system internal energy is constant.

Assertion : For an isolated system mechanical energy is conserved. 
Reason : Kinetic frictional force is absent for an isolated system.