The ball was thrown vertically downward at a speed of 5 m / s. How high will this ball bounce after hitting the floor

The ball was thrown vertically downward at a speed of 5 m / s. How high will this ball bounce after hitting the floor if the height from which it was thrown was 2.5 m? The loss of energy on impact is negligible.

Let’s find the fall time. h = Vot + gt ^ 2/2; 3 = 6t + 5t ^; 5t ^ 2 + 6t-3 = 0; D = 36 + 60 = 96 = (9.8) ^ 2; t = -6 + 9.8 / 10 = 0.38 s; Speed before falling and after rebound with elastic impact V = Vo + gt = 6 + 10 * 0.38 = 9.8 m / s, movement time after rebound (v-vo) / t = g, t = 9.8 / 10 = 0.98 s, lifting height H = 9.8 * 0.98-5 * 0.98 * 0.98 = 4.8 m.
It can be solved using the law of conservation of energy: before hitting the ground mv2 ^ 2/2-mv1 ^ 2/2 = mgh; v2 ^ 2/2 = (gh + v1 ^ 2/2); after the rebound, the body will rise mgH = mv2 ^ 2/2; H = (gh + v1 ^ 2/2) / g = (10 * 3 + 6 * 6/2) / 10 = 48/10 = 4.8 m