From what height should hail fall with a temperature of 0 ° C for the hailstones to melt on the ground? Disregard air resistance?

Decision:
Obviously, the hailstones will melt when they reach the temperature required to melt. It is reached at the moment when the potential energy reaches the same value.
Let’s write two formulas:
En = Q;
Ep = m * g * h;
Next, we express the amount of heat through another formula: Q = lambda * m. We get then that En = lambda * m.
We need to equate the right-hand sides of both formulas.
lambda * m = mgh.
Then we will reduce by m and get:
lambda = gh.
Next, you need to express the height h.
h = lambda / g.
Substitute the known values. We take into account that the lambda value is always the same, it is equal to 334000 (We are looking for it in the table under the ice value).
h = 334000/10 = 33400 m.
For convenience, let’s translate into kilometers: h = 33.4 km.
Answer: 33.4