1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Ierofanga [76]
3 years ago
10

Calculate the energy needed to heat 4 kg of water from 25°C to 45°C.

Physics
2 answers:
inna [77]3 years ago
8 0
(1 cal/g °C) x (4000 g) x (45 - 25)°C = 80000 cal = 80 kcal. So the answer is 80 kcal .
melisa1 [442]3 years ago
4 0

Answer:

80 Kcal

Explanation:

Specific heat is the energy required to raise the temperature of a unit mass of a substance by one degree. Its units are kJ/kg·K or kJ/kg·°C in the SI system.

There are two types of specific heat: 1) when the process is at constant volume. 2) When it's at constant pressure. In the case of liquids, the value is the same for the two cases. The specific heat of water is equal to 4.18kJ/kg·°C (in that range of temperatures)

The formula which relates energy needed, specific heat, change in temperature, and mass of the substance is the following:

ΔU=m·c·(T2-T1)

T2: final temperature of the substance

T1: initial temperature of the substance

c: specific heat of the substance

m: the mass of the substance

ΔU: energy required to raise the temperature the substance from T1 to T2

Plugging the given values values on the equation:

ΔU=4kg·(4.18kJ/kg·°C)·(45°C-25°C)

ΔU=334.4kJ

Now, it only rests to convert from kJ to cal:

1kJ=0.2390kcal

So:

334.4kJ=334.4*0.2390kcal=79.9kcal≈80kcal

So the energy needed to heat 4 kg of water from 25°C to 45°C is 80kcal

You might be interested in
What is a car doing as it rounds a curve
andriy [413]

Answer:

its direction is changing

4 0
2 years ago
Which is not true of friction? A. Causes wear and tear of the surfaces B. Helps us to fall easily on roads C. Produces heat D. P
Ganezh [65]

Answer:

B.

Hope this helps

5 0
2 years ago
Read 2 more answers
A cylindrical resistor element on a circuit board dissipates 1.2 W of power. The resistor is 2 cm long, and has a diameter of 0.
34kurt

Answer:

(a) The resistor disspates 103680 joules during a 24-hour period.

(b) The heat flux of the resistor is approximately 4340.589 watts per square meter.

(c) The fraction of heat dissipated from the top and bottom surfaces is 0.045.

Explanation:

(a) The amount of heat dissipated (Q), measured in joules, by the cylindrical resistor is the power multiplied by operation time (\Delta t), measured in hours. That is:

Q = \dot Q \cdot \Delta t (1)

If we know that \dot Q = 1.2\,W and \Delta t = 86400\,s, then the amount of heat dissipated by the resistor is:

Q = (1.2\,W)\cdot (86400\,s)

Q = 103680\,J

The resistor disspates 103680 joules during a 24-hour period.

(b) The heat flux (Q'), measured in watts per square meter, is the heat transfer rate divided by the area of the cylinder (A), measured in square meters:

Q' = \frac{\dot Q}{A} (2)

Q' = \frac{\dot Q}{\frac{\pi}{2}\cdot D^{2}+\pi\cdot D \cdot h } (3)

Where:

D - Diameter, measured in meters.

h - Length, measured in meters.

If we know that \dot Q = 1.2\,W, D = 4\times 10^{-3}\,m and h = 2\times 10^{-2}\,m, the heat flux of the resistor is:

Q' = \frac{1.2\,W}{\frac{\pi}{2}\cdot (4\times 10^{-3}\,m)^{2}+\pi\cdot (4\times 10^{-3}\,m)\cdot (2\times 10^{-2}\,m) }

Q' \approx 4340.589\,\frac{W}{m^{2}}

The heat flux of the resistor is approximately 4340.589 watts per square meter.

(c) Since heat is uniformly transfered, then the fraction of heat dissipated from the top and bottom surfaces (r), no unit, is the ratio of the top and bottom surfaces to total surface:

r = \frac{\frac{\pi}{2}\cdot D^{2}}{A} (3)

If we know that A \approx 2.765\times 10^{-4}\,m^{2} and D = 4\times 10^{-3}\,m, then the fraction is:

r = \frac{\frac{\pi}{2}\cdot (4\times 10^{-3}\,m)^{2} }{2.765\times 10^{-4}\,m^{2}}

r = 0.045

The fraction of heat dissipated from the top and bottom surfaces is 0.045.

7 0
3 years ago
A cat with a mass of 4.50 kilograms sits on a ledge 0.800 meters above the ground. If it jumps to the ground, how much kinetic e
Slav-nsk [51]
Answer:

The cat will have <span>36J</span> of kinetic energy.

5 0
3 years ago
Read 2 more answers
A piece of wood on top of an ocean wave stays in the same location, only moving up and down as the wave passes. It is energy tha
Ierofanga [76]

Answer:

Hey

Yes, this is true.

As some people have it wrong, waves in the water (ocean) are not waves of moving water, rather the wave is moving through the water. A wave is a disturbance of a medium not the meduim moving.

8 0
3 years ago
Other questions:
  • All of the fallowing are possible sources of error in a scientific investigation exept for
    9·1 answer
  • An electric current is created in a long thin wire. How will increasing the current and changing the direction of the current ef
    6·2 answers
  • In the first-order spectrum, maxima for two different wavelengths are separated on the screen by 3.40 mm . what is the differenc
    11·1 answer
  • Which is an example of chemical energy from batteries to electromagnetic ( light ) energy?
    9·1 answer
  • What happens when oxygen reacts with sodium?
    10·1 answer
  • Two bumper cars move in a straight line with the following equations of motion: x1 = -4.0 m + (1.1 m/s )t x2 = 8.8 m + (-2.9 m/s
    12·1 answer
  • You drop a penny from the top of the Salesforce building in San Francisco. If the
    5·1 answer
  • (12 points) Analysis from the point where the block is released to the point where it reaches the maximum height i) Calculate th
    7·1 answer
  • The same force that causes a pop fly to smack into your baseball mitt keeps the Moon in its orbit around Earth. Agree Disagree E
    14·1 answer
  • Billy ran 800m in 240s. What is his speed? Round to two decimal places <br> Your answer
    6·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!