A ball is bouncing vertically between a floor and ceiling, which are both horizontal and separated by 4 \mathrm{~m}. All collisions are perfectly elastic, and when the ball hits the floor, it has a speed of 12 \mathrm{~m} / \mathrm{s}. How long does a complete up-down cycle take?
Answer Choices
A. 0.3 \mathrm{~s}
B. 0.4 \mathrm{~s}
C. 0.6 \mathrm{~s}
D. 0.8 \mathrm{~s}
E. 2.4 \mathrm{~s}