Consider the following two statements: 1. Linear momentum of a system of particles is zero 2. Kinetic energy of a system of particles is zero Then
Correct Answer :
1 does not imply 2 but 2 implies 1
Solution :
The correct option is: 1 does not imply 2 but 2 implies 1
Let us analyze the two statements step-by-step to understand the logical relationship between them.
Statement 1: Linear momentum of a system of particles is zero.
The total linear momentum of a system of particles is the vector sum of the individual linear momenta of the particles:
If the total linear momentum is zero (), it means the vector sum of the individual momenta is zero. This does not require each individual velocity to be zero. For example, in a two-particle system, if one particle moves with velocity and another identical particle moves with velocity , the total linear momentum is:
However, since the particles are in motion, the total kinetic energy of the system is:
Thus, Statement 1 does not imply Statement 2.
Statement 2: Kinetic energy of a system of particles is zero.
The total kinetic energy of a system of particles is the sum of the individual kinetic energies:
Since mass is always positive and the term is non-negative, the kinetic energy of each particle is non-negative (). For the sum of non-negative terms to be zero, each individual term must be zero:
for all . Since all particles are at rest, their individual linear momenta are also zero:
Consequently, the total linear momentum of the system must be zero:
Thus, Statement 2 implies Statement 1.
Therefore, Statement 1 does not imply Statement 2, but Statement 2 implies Statement 1.
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