Suppose we define a quantity ‘Linear Momentum’ as linear momentum = mass x speed. The linear momentum of a system of particles is the sum of linear momenta of the individual particles. Can we state a principle of conservation of linear momentum as “linear momentum of a system remains constant if no external force acts on it”?

Question

Philoid · Accepted Answer

Since we are using speed in the definition of linear momentum, so the linear momentum of a system of particles in this case is just the algebraic sum of the linear momentum of the individual particles. So, the principle of conservation of linear momentum does not hold true for every scenario here because we are not using the direction of the velocity of the particles.