If the average speed of a car is 45 km/jr, how far can it travel in 40 minutes?

3. If nothing can ever be at absolute zero, why does the concept exist?

Tanzania [10]

The absolute zero in temperature refers to the minimal possible temperature. It is the temperature at which the molecules of a system stop moving, so it is a really useful reference point.

<h3>Why absolute zero can't be reached?</h3>

It would mean that we need to remove all the energy from a system, but to do this we need to interact with the system in some way, and by interacting with it we give it "some" energy.

Actually, from a quantum mechanical point of view, the absolute zero has a residual energy (so it is not actually zero) and it is called the "zero point". This happens because it must meet Heisenberg's uncertainty principle.

So yes, the absolute zero can't be reached, but there are really good approximations (At the moment there is a difference of about 150 nanokelvins between the absolute zero and the smallest temperature reached). Also, there are a lot of investigations near the absolute zero, like people that try to reach it or people that just need to work with really low temperatures, like in type I superconductors.

So, concluding, why does the concept exist?

Because it is a reference point.
It is the theoretical temperature at which the molecules stop moving, defining this as the minimum possible temperature.

If you want to learn more about the absolute zero, you can read:

brainly.com/question/3795971

3 0

2 years ago

Water flows through a converging pipe at a mass flow rate of 25 kg/s. If the inside diameter of the pipes sections are 7.0 cm an

ser-zykov [4K]

Answer:

volumetric flow rate = $0.0251 m^3/s$

Velocity in pipe section 1 = $6.513m/s$

velocity in pipe section 2 = 12.79 m/s

Explanation:

We can obtain the volume flow rate from the mass flow rate by utilizing the fact that the fluid has the same density when measuring the mass flow rate and the volumetric flow rates.

The density of water is = 997 kg/m³

density = mass/ volume

since we are given the mass, therefore, the volume will be mass/density

25/997 = $0.0251 m^3/s$

volumetric flow rate = $0.0251 m^3/s$

Average velocity calculations:

Pipe section A:

cross-sectional area =

$\pi \times d^2\\=\pi \times 0.07^2 = 3.85\times10^{-3}m^2$

mass flow rate = density X cross-sectional area X velocity

velocity = mass flow rate /(density X cross-sectional area)

$velocity = 25/(997 \times 3.85\times10^{-3}) = 6.513m/s$

Pipe section B:

cross-sectional area =

$\pi \times d^2\\=\pi \times 0.05^2= 1.96\times10^{-3}m^2$

mass flow rate = density X cross-sectional area X velocity

velocity = mass flow rate /(density X cross-sectional area)

$velocity = 25/(997 \times 1.96\times10^{-3}) = 12.79m/s$

7 0

3 years ago

A thermoelectric refrigerator is powered by a 16-V power supply that draws 2.9 A of current. If the refrigerator cools down 3.1

Viktor [21]

Answer:

COP = 0.090

Explanation:

The general formula for COP is:

COP = Desired Output/Required Input

Here,

Desired Output = Heat removed from water while cooling

Desired Output = (Specific Heat of Water)(Mass of Water)(Change in Temperature)/Time

Desired Output = [(4180 J/kg.k)(3.1 kg)(25 - 11)k]/[(12 hr)(3600 sec/hr)]

Desired Output = 4.199 W

And the required input can be given as electrical power:

Required Input = Electrical Power = (Current)(Voltage)

Required Input = (2.9 A)(16 V) = 46.4 W

Therefore:

COP = 4.199 W/46.4 W

COP = 0.090

8 0

3 years ago

You have been assigned to design an open cylindrical storage tank 4 meters tall with a diameter of 8 meters to be made out of A-

Katen [24]

Answer:

The required wall thickness is $1.506 \times 10^{-3}$ m

Explanation:

Given:

Fluid density $\rho = 1200$ $\frac{kg}{m^{3} }$

Diameter of tank $d = 8$ m

Length of tank $l = 4$ m

F.S = 4

For A-36 steel yield stress $\sigma = 250$ MPa,

Allowable stress $\sigma _{allow} = \frac{\sigma}{F.S}$

$\sigma _{allow} = \frac{250}{4} = 62.5$ MPa

Pressure force is given by,

$P = \rho gh$

$P = 1200 \times 9.8 \times 4$

$P = 47088$ Pa

Now for a vertical pipe,

$\sigma _{allow} = \frac{Pd}{4t}$

Where $t =$ required thickness

$t = \frac{Pd}{4 \sigma _{allow} }$

$t = \frac{47088 \times 8 }{4 \times 62.5 \times 10^{6} }$

$t = 1.506 \times 10^{-3}$ m

Therefore, the required wall thickness is $1.506 \times 10^{-3}$ m

8 0

3 years ago

Explain how potential energy converts to kinetic energy in the loop-the-loop section of the roller coaster. Make sure to note wh

larisa86 [58]

Answer:

lol

Explanation:

8 0

3 years ago