# Principle of conservation of energy - conservative force

Q.  According to the principle of conservation of energy, under the action of _________ force, the sum of P.E and K.E of a particle remains constant.
- Published on 21 Sep 15

a. conservative force
b. dissipative force
c. frictional force
d. air resistance force

#### Discussion

• Sravanthi   -Posted on 15 Dec 15
- Conservative force: If the work done by a particle is independent of the path followed from position 1 to position 2 is said to be conservative.

- Gravity force, spring force, elastic force are examples of conservative force.

- The work done is stored as potential energy, if a particle moves under the action of conservative force.

- Here, work done is equal to negative change in potential energy.

Considering work-energy principle,

Work done is equal to change in kinetic energy (U = [(K.E)2 – (K.E)1]) -------------- (1)

Considering action of conservative forces, (U = [- (P.E)2 – (P.E)1]) --------------- (2)

From (1) and (2),

(KE1 + PE1) = (KE2 + PE2)

Hence, it is proved that, according to the principle of conservation of energy, under the action of conservative force force, the sum of P.E and K.E of a particle remains constant.

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