Consider the following statements: 1. There is no net moment on a body which is in equilibrium. 2. The momentum of a body is always conserved. 3. The kinetic energy of an object is always conserved. Which of the statement(s) given above is/are correct?

CDS 2018 PYQ with Answer — Consider the following statements: 1. There is no net moment on a bod…

2018 · Q10

Consider the following statements:

1There is no net moment on a body which is in equilibrium.
2The momentum of a body is always conserved.
3The kinetic energy of an object is always conserved.

Which of the statement(s) given above is/are correct?

General KnowledgePhysics

A1, 2 and 3
B2 and 3 only
C1 and 2 only
D1 only

Explanation

Statement 1 is true: a body at rest has zero kinetic energy, while a moving body has non-zero velocity, so the possibilities it asserts hold. Statement 2 is false: momentum is conserved only for an isolated system, and a body acted on by an external force gains or loses momentum, so it is not always conserved. Statement 3 is false: kinetic energy is routinely dissipated, for example as heat in inelastic collisions, so it is not always conserved either. Only statement 1 is correct.