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Kipish [7]
3 years ago
11

The video shows a collapsing cloud of interstellar gas, which is held together by the mutual gravitational attraction of all the

atoms and molecules that make up the cloud. as the cloud collapses, the overall force of gravity that draws the cloud inward because .
Physics
1 answer:
Aleonysh [2.5K]3 years ago
5 0
The overall force of gravity becomes stronger and stronger. This is because the gravity depends on the inverse of the square of the distance:
F=G \frac{m_1 m_2}{r^2}
and since the distance r between the molecules becomes smaller, the gravity increases more and more.
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An ultrasonic ruler, such as the one discussed in Example 4 in Section 16.6, displays the distance between the ruler and an obje
garik1379 [7]

Answer:

reading would be 5.413 m.

Explanation:

Given:-

- The actual distance from ruler to an object is d = 24.0 m

- The adiabatic bulk modulus, B = 2.37 *10^9 Pa

- The density of seawater, ρ = 1025 kg/m^3

- The preset value of speed of sound in air, v_th = 343 m/s.

Find:-

Determine the distance reading that the ruler displays.

Solution:-

- We will first determine the actual speed of the sound ( v_a) in sea-water which can be determined from the following formula:

                            v_a = √ (B /  ρ )

- Plug in the values in the relationship above and compute v_a:

                            v_a = √ ( 2.37 *10^9 /  1025  )        

                            v_a = 1520.59038 m/s

- The time taken (t) for for the sound to travel from source(ruler) to an object which is d distance away.

                            d = v_a*t

                            t = d / v_a

                            t = 24.0 / 1520.59038

                            t = 0.01578 s

- The distance reading on the ruler would be preset speed (v_th) of sound in air multiplied by the time taken(t).

                           reading = v_th*t

                           reading = (343)*(0.01578)

                                         = 5.413 m

6 0
3 years ago
A fluid is flowing through a circulat tube at 0.4 kg/s. Tube inner surface is smooth with a diameter 0.014 m. Fluid density is 9
ElenaW [278]

Answer:

The convection coefficient is 15456.48\ W/m^{2}K

Solution:

Mass flow rate, \dot{m} = 0.4\ kg

Inner diameter of the tube, d = 0.014 m

Fluid density, \rho_{f} = 990\ kg/m^{3}

Specific Heat, C = 3845 J/K

Thermal Conductivity, K = 0.74

Prandtl Number, P_{r} = 8.6

Heat flux, \dot{q} = 71,297\ W/m^{2}

Viscosity, \mu = 0.00079\ Ns/m^{2}

Now,

To calculate the convection heat coefficient, h:

Determine the cross sectional area of the circular tube:

A_{c} = \frac{\pi}{4}d^{2} = \frac{\pi}{4}\times (0.014)^{2} = 1.54\time 10^{- 4}\ m^{2}

Determine the velocity of the fluid inside the tube by mass flow rate:

\dot{m} = \rho_{f}A_{c}v

0.4 = 990\times 1.54\time 10^{- 4}v

v = 2.624 m/s

Determine the Reynold's Number, R_{e}:

R_{e} = \frac{\rho_{f}dv}{\mu}

R_{e} = \frac{990\times 0.014\times 2.624}{0.00079} = 46036.253

Thus it is clear that R_{e} > 10,000 hence flow is turbulent.

Now,

Determine the Nusselt Number:

N_{u} = 0.023R_{e}^{0.8}P_{r}^{0.4}

N_{u} = 0.023\times 46036.253^{0.8}\times 8.6^{0.4} = 292.42

Also,

N_{u} = \frac{dh}{K}

where

h = convection coefficient

Now,

292.42 = \frac{0.014\times h}{0.74}

h = 15456.48\ W/m^{2}K

7 0
3 years ago
In Kepler's model of the solar system, the planets move around the Sun in _________ orbits.
cestrela7 [59]
B. elliptical.

The planets move in elliptical orbits round the Sun.
3 0
3 years ago
At exactly 3:14PM, the velocity of a dog running in a park points toward a group of flowers. Which of the following best describ
dmitriy555 [2]

Answer:

Options A, B, and C are all possible.

Explanation:

We know that the instantaneous velocity of the dog at 3:14PM is possitive to toward the flowers. But what about the acceleration to toward the flowers?

If the dog is decreasing speed at 3:14PM, it means that acceleration is negative toward the flowers, hence (since F=ma) the net force points away from the flowers.

If the dog is increasing speed at 3:14PM, it means that acceleration is positive toward the flowers, hence (since F=ma) the net force points toward the flowers.

If the dog is not increasing nor decreasing speed at 3:14PM, it means that acceleration is 0, hence (since F=ma) the net force is null and it does not point neighter to toward the flowers  nor away from the flowers. This happens when the forces acting on the dog are equal to both sides.

4 0
3 years ago
Given the frequency of an electromagnetic wave, what else can you find immediately?
Oksana_A [137]

Answer:

wavelength

Explanation:

An electromagnetic waves is produced due to interaction of oscillating electric and magnetic field when they interacts perpendicular to each other. For example, Gamma rays, X rays , ultraviolet rays, visible radiations, infrared rays, micro waves, radio waves.

All the electromagnetic waves have velocity equal to velocity of light.

If the frequency of electromagnetic wave is unknown then we find the wavelength of wave. the formula used is

Wave speed = wavelength x frequency

3 0
3 years ago
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