Physics, 30.01.2021 14:00 lola5683

hot water is added to three times its mass of water at 10 degree celsius and the resulting temperature is 20 degrees Celsius What is the initial temperature of the hot water

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Answer from: ttaysia

The initial temperature of the hot water is $50\; \rm ^{\circ} C$ (assuming that no heat was lost to the surroundings.)

Explanation:

Let denote the mass of the hot water.

The question states that the mass of the water at $10\; \rm ^\circ C$ is three times the mass of the hot water. If the mass of the hot water is , the mass of the cold water would be $3\, m$ .

Let denote the specific heat capacity of water. Let denote the mass of some water. The energy required to change the temperature of that much water by $\Delta T$ (without state change) would be:

$Q = c \cdot m \cdot \Delta T$ .

The temperature change for the cold water was:

$\Delta T_1 = 20\; \rm ^{\circ} C - 10\; \rm ^{\circ} C = 10\; \rm K$ .

Energy required to raise the temperature of water with mass $3\, m$ from $10\; \rm ^{\circ} C$ to $20\; \rm ^{\circ} C$ :

$Q_1 = c \cdot (3\, m) \cdot (10\; \rm K)$ .

On the other hand, if the initial temperature of the hot water is $t\; \rm ^{\circ} C$ (where t 20 ,) the temperature change would be:

$\Delta T_2 = t\; {\rm ^{\circ} C} - 20\; {\rm ^{\circ} C} = (t - 20)\; {\rm K}$ .

Calculate the energy change involved:

$Q_2 = c \cdot m \cdot ((t - 20)\; \rm K)$ .

If no energy was lost to the surroundings, Q_1 should be equal to Q_2 . That is:

$c \cdot (3\, m) \cdot (10\; {\rm K}) = c\cdot m \cdot ((t - 20)\; {\rm K})$ .

Simplify and solve for :

t - 20 = 30 .

t = 50 .

Therefore, the initial temperature of the hot water would be $50\; {\rm ^\circ C}$ .

Answer from: Quest

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Answer from: Quest

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

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hot water is added to three times its mass of water at 10 degree celsius and the resulting temperatu...