A \(0.20-\mathrm{kg}\) softball is traveling at a velocity of \(20 \mathrm{~m} / \mathrm{s}\) to the east relative to Earth. It collides head-on with a 0. 40 \(\mathrm{kg}\) rubber ball traveling at a velocity of \(10 \mathrm{~m} / \mathrm{s}\) to the west.

(a) If the system's kinetic energy, as measured from the Earth reference frame, decreases by \(20 \%\) because of the collision, what are the final velocities of the balls?

(b) What change in internal energy has occurred?

(c) An observer watches this collision from a reference frame moving at a velocity of \(15 \mathrm{~m} / \mathrm{s}\) to the east relative to the Earth reference frame. What changes in kinetic and internal energies does this observer measure?

(d) What changes in kinetic and internal energies would be measured by an observer in a reference frame traveling at \(20 \mathrm{~m} / \mathrm{s}\) east relative to the Earth reference frame?