UPSC CDS 1 2018 GK Paper

Among the given statements, only statement 1 is correct.
The law of moments (also called the law of the lever) is stated as follows: when a body is in equilibrium the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point. There is no net moment on a body which is in equilibrium. Momentum is always conserved in a closed system. Momentum is not conserved if there is friction or gravity.
Hence, statement 2 is incorrect. Energy is conserved only in elastic collision. Energy is not conserved in inelastic collision. So, we cannot say energy is always conserved. Hence, statement 3 is not correct.