- Consider the following statements Assertion (A): In an elastic collision of two billiard balls, the total kinetic energy is conserved during the short time of collision of the balls (i.e., when they are in contact) : Energy spent against friction does not follow the law of conservation of energy of these statements. Reason (R) (a) Both A and R are true and the R is a correct explanation of A. (b) Both A and R are true but the R is not a correct explanation of the A. (c) A is true but the R is false. (d) Both A and R are false.