Work, Energy and Power · Question 26

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R In the light of the above statements, choose the most appropriate answer from the options given below

1. A is false but R is true
2. Both A and R are true but R is NOT the correct explanation of A
3. A is true but R is false
4. Both A and R are true and R is the correct explanation of A

Answer

(2) Both A and R are true but R is NOT the correct explanation of A

Solution

A central force has the form F = f(r) r (e.g. gravitational, electrostatic force).

dW = F d r = f(r) dr W = r1r2 f(r) dr, which depends only on the end points.

The work done is independent of the path (the force is conservative). A is true.

A potential energy can be defined only for conservative forces; friction and viscous forces are non-conservative and have no potential energy. R is true.

But R does not explain why a central force does path-independent work.

Answer: (2)