Question

What is true in general when two particles collide

• A. the relative velocity of first particle w.r.t. second before and after collision remains the same
• B. the relative velocity of first particle w.r.t. second after collision is equal or less than opposite to the relative velocity before collision
• C. kinetic energy of particles after collision is equal to kinetic energy of particles after collision
• D. kinetic energy of particles after collision in inelastic collision is always greater than kinetic energy before collision

Answer 1

The correct option is B the relative velocity of first particle w.r.t. second after collision is equal or less than opposite to the relative velocity before collision

When the particles approach and collide, depending on the coefficient of restitution, their departing is decided. If the collision is elastic, since no energy is lost, they depart with same relative speeds. But when it isn't elastic; there is loss in energy thus leaving lesser KE and lesser speeds of departing.