A solar water heater is used to heat 40 kg of water. When the water temperature increases from 10℃ t

(1) Heat absorbed by water:

Absorption Q=cm△t=4.2×103J/(kg?℃)×40kg×(30℃-10℃)=3 .36×106J;< /p>

(2) From the question, Q suction = Q release × 20% = m′q × 20% = 3.36 × 106J,

The required mass of each:

< p>m′==

Q put

q×20%

3.36×106J

3×107J/kg×20%

= 0.56 kg.

Answer: The heat absorbed by the water is 3.36 × 106 J; approximately 0.56 kg of coal must be burned.

A solar water heater, some parameters on the nameplate are shown in the table below. Fill it with water and place it on a sunny horizontal platform(1) If its pedal is horizontal

(1) The solar energy absorbed by the water is:

Q absorption = cm1△t

= 4.2×103J/(kg?℃)×50kg×(60℃-20℃)

=8.4×106J

( 2) Q Suction = Q and discharge = Vq,

Then the heat is equivalent to the gas saved V=

< tr>< /table>=≈0.215 m3,

(3) When solar energy is used to directly heat water, it is easy to obtain, safe and clean, and will not cause pollution to the environment. Therefore, the advantages of solar energy are convenience, safety, cleanliness andabsence of pollution, and it is an ideal energy source for the future.

Answer: The solar energy absorbed by water is 8.4 × 106 J; this is equivalent to a saving of 0.215 m3 of gas;

The advantages of solar energy are convenience, safety, cleanliness and no gas. pollution, which is ideal for the energy of the future.

Solar energy is a huge source of energy, its total radiation power is 3.8 × 1023 kW, that is, the heat radiated to the surrounding space per second is equivalent to the standard of 1.3 × 1019 kg

Q put

q

8.4×106J

3.9×107J/m3

(1) Mass of water: m=ρV=1000×80×10 -3 m 3 =80Kg Pressure: F="G=mg=(80" Kg +40 Kg) ×10N/ Kg =1200N (1 point) Pressure: P=F /s=1200N/0.2m 2 =6000Pa (1 point) (2) Heat absorbed by water: Q=2.8×10 6 J×1.5×8×60% =2.016×10 7 J (1 point) Increase in temperature: Δt= Q/cm=2.016×10 7 J/ 4.2×10 3 Kg/m 3 ×80kg=60℃( 2 points) (3) m=Q/q=2.016×107 J/4.2×10 7 J/Kg=0.48 Kg (2 points)

Mass of water: m=ρV=1000×80×10 -3 m 3 =80Kg Pressure: F="G=mg=(80" Kg +40 Kg) ×10N/ Kg =1200N The pressure of the solar water heater on the counter: P=F/s=1200N /0.2m 2 =6000Pa;Calculate the heat absorbed by the water according to the formula Q=cmt: Q=2.8×10 6 J× 1.5×8×60%=2.016×10 7 J of increased temperature: Δt= Q/cm=2.016×10 7 J/4.2×10 3 Kg/m 3 ×80kg=60℃. If the solar energy received by the water heater during a day is obtained by burning coal gas (calorific value q ="4.2" x 10 7 J/kg), The mass of gas required to be completely burned is m=Q/q= 2.016×10 7 J/4.2×10 7 J/Kg=0.48Kg

(1) From the meaning of the question we can see that the sun moves in the surrounding space every second Radiated heat:

Q=m coal q=1.3 ×1019kg×3.4×107J/kg=4.42×1026J

< p>(2) From the meaning of the question, we see that the heatr absorbed by the water:

Q suction = Q = 4.42×1026J,

According to Q suction = cm (t-t0), the mass of heatable water can be obtained:

mwater=

< /tr>

Aspiration Q

c( t?t0)

=< td style="padding-top:1px;font- size:90%">4.2×103J/(kg?℃)×(55℃?15℃)

4.42×1026J

≈2.63×1021kg=2.63×1018t.

Answer: The heat radiated by the sun to the surrounding space per second is 4.42×1026J. This energy can increase the temperature of 2.63×1018t of water from 15℃ to 55℃.