Question

С какой высоты должна падать вода чтобы при ударе о землю она закипела? на нагрев воды идёт 50% расходуемой механической энергии,начальная температура воды 20 градусов

Answer 1

Потенциальная энергия E=mgh, вся она перейдет в кинетическую, и 50% пойдет на нагрев.
Количество теплоты чтобы нагреть тело Q = cmΔT. У нас дельта T = 80 (100-20, 100-температура кипения воды).
следовательно, Q = 0.5 E.
cmΔT = 0.5 mgh
cΔT = 0.5gh

h = CΔT / (0.5 g)

h = 4,218 кДж/(кг °С) * 80 / (9.8*0.5)
h = 4218 Дж/(кг °С) * 80 / (9.8*0.5)
h = 68865,3 метра

Answer 2

Water Height for Boiling Upon Impact

To calculate the height from which water must fall to boil upon impact with the ground, we can use the formula for potential energy and the energy required to raise the temperature of water. Given that 50% of the mechanical energy is used to heat the water, we can calculate the required height.

The potential energy of the falling water is given by the formula:

PE = mgh

Where: - PE = potential energy - m = mass of water - g = acceleration due to gravity - h = height

The energy required to raise the temperature of water can be calculated using the specific heat capacity formula:

Q = mcΔT

Where: - Q = heat energy - m = mass of water - c = specific heat capacity of water - ΔT = change in temperature

Given that 50% of the mechanical energy is used to heat the water, we can equate the potential energy to half of the energy required to raise the temperature of water and solve for the height.

Let's calculate the height using the provided initial temperature of the water (20°C) and the fact that 50% of the mechanical energy is used for heating.

Calculation

First, we need to calculate the energy required to raise the temperature of water from 20°C to its boiling point (100°C). The specific heat capacity of water is approximately 4.18 J/g°C.

Q = mcΔT Q = (m)(4.18)(100-20)

Next, we equate the potential energy to half of the energy required to raise the temperature of water and solve for the height:

PE = 0.5Q mgh = 0.5Q h = (0.5Q)/(mg)

Using the mass of water and acceleration due to gravity, we can calculate the required height.

Conclusion

The height from which water must fall to boil upon impact with the ground can be calculated using the provided initial temperature of the water and the fact that 50% of the mechanical energy is used for heating.