Two identical particles move toward each other, one twice as fast as the other. Just before they collide, one has a kinetic energy of 25 J and the other 50 J. At this instant their total kinetic energy is

Question

Quizplus · Accepted Answer

Since one particle is moving twice as fast as the other, it has four times the kinetic energy of the other particle. Therefore, if the slower particle has a kinetic energy of 25 J, then the faster particle has a kinetic energy of 100 J (4 times 25 J). Just before they collide, their total kinetic energy is the sum of their individual kinetic energies, which is 25 J + 100 J = 125 J. After the collision, their kinetic energies will be redistributed, but their total kinetic energy remains constant, so the total kinetic energy just before the collision is 125 J.

Two Identical Particles Move Toward Each Other, One Twice as Fast