(2) A sphere A of mass m1 moving with speed υ1 collides centrally and elastically with a stationary sphere B of mass m2. The rate of change of the kinetic energy of sphere A depends on: a) from the time that the impact of the spheres lasts.
b.) from the initial momentum of the sphere A.
c). from the masses of the spheres
.d) from the initial velocity of the sphere A.

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(3)During the central and elastic impact of two spheres, the difference of their velocities before the impact is:
a) greater than the difference of their speeds after the impact
b) equal to the difference of their speeds after the impact
c) less than the difference of their speeds after the impact
d) opposite to the difference of their speeds after the impact

choose the correct answer