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abruzzese [7]
3 years ago
7

Consider a spherical volume of space that is large enough to be considered homogeneous. Also consider a particle on the surface

of this volume that is moving away from the center with the Hubble flow. Assuming that the pressure within the volume is negligible, the universe will re-collapse if the particle's Hubble speed is: A. Greater than its escape speed from the mass within the volume B. The same as its escape speed from the mass within the volume C. Less than its escape speed from the mass within the volume
Physics
1 answer:
LenKa [72]3 years ago
3 0

Answer:

Option A applies.

A.  Greater than its escape speed from the mass within the volume

Explanation:

Here it is mentioned that the spherical volume is large enough for the space to be considered as homogeneous. Also, the pressure within the volume is negligible, so that will not result into the re collapse of the Universe. Now as per our knowing, Hubble's Law relates the average speed of the particle to the distance R between the Earth and the particle. So, if the particle's speed is greater than it's escape speed from the mass within the volume, then the Universe is bound to re collapse back again. Option A applies.

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A 5 kgkg sphere having a charge of ++ 8 μCμC is placed on a scale, which measures its weight in newtons. A second sphere having
Mrac [35]

Answer:

 F_Balance = 46.6 N    ,m' = 4,755 kg

Explanation:

In this exercise, when the sphere is placed on the balance, it indicates the weight of the sphere, when another sphere of opposite charge is placed, they are attracted so that the balance reading decreases, resulting in

          ∑ F = 0

          Fe –W + F_Balance = 0

         F_Balance = - Fe + W

           

The electric force is given by Coulomb's law

          Fe = k q₁ q₂ / r₂

The weight is

          W = mg

Let's replace

           F_Balance = mg - k q₁q₂ / r₂

Let's reduce the magnitudes to the SI system

          q₁ = + 8 μC = +8 10⁻⁶ C

          q₂ = - 3 μC = - 3 10⁻⁶ C

          r = 0.3 m = 0.3 m

Let's calculate

         F_Balance = 5 9.8 - 8.99 10⁹  8 10⁻⁶ 3 10⁻⁶ / (0.3)²

         F_Balance = 49 - 2,397

         F_Balance = 46.6 N

This is the balance reading, if it is calibrated in kg, it must be divided by the value of the gravity acceleration.

Mass reading is

          m' = F_Balance / g

          m' = 46.6 /9.8

          m' = 4,755 kg

6 0
3 years ago
Why might surface mining be less risky for miners than underground mining?
aev [14]
Surface miners work aboveground. (Apex) ^-^

6 0
3 years ago
Read 2 more answers
Damping is negligible for a 0.135-kg object hanging from a light, 6.30-N/m spring. A sinusoidal force with an amplitude of 1.70
IceJOKER [234]

Answer:

0.72 Hz minimum frequency

Explanation:

When the damping is negligible,Amplitude is given as

A = (F/m)/[\sqrt{(\omega ^{^{2}}-\omega _{o}^{2}})^2

here \omega _{o}^{2}= k/m = (6.30)/(0.135) = 46.67 N/m kg

F / mA = 1.70/(0.135)(0.480) = 26.2 N/m kg

From the above equation , rearranging for ω,

\omega ^{2}= \omega _{o}^{2}\pm F/m

⇒ ω² =46.67 ± 26.2 = 72.87 or 20.47

⇒ ω = 8.53 or 4.52 rad/s

Frequency = f

ω=2 π f

⇒ f = ω / 2π =  8.53 /6.28  or 4.52 / 6.28 = 1.36 Hz or 0.72 Hz

The lower frequency is 0.72 Hz and higher is 1.36 Hz

8 0
3 years ago
A cheetah runs 5 miles in 60 seconds. How fast did the cheetah run in MILES per HOUR? Convert seconds into hours first, then sol
Vinil7 [7]

Answer:

300 miles per hour

Explanation:

Speed is distance per unit time, expressed as s=d/t where t is the time taken, d is distance covered and s is the speed.

Convering s to hrs

To convert seconds to hours, we knkw that 1 hour has 60 minutes and each minute has 60 seconds. Therefore, 1 hour has 60*60=3600 seconds

If 3600s=1 h

60 s=?

By cross multiplication 60s*1 h/3600s=1/60 hours

Given distance as 5 miles and time as 1/60 hours then the speed will be 5 divided by 1/60 hrs which is equivalent to 5*60=300 miles per hour

6 0
3 years ago
"A ball with a mass of 0.1 kg is rolling at a velocity of 5 m/s. What is its
Mumz [18]

Answer:

velocity

Explanation:

because the si unit of mass is kg, velocity is m/s, acceleration is m/S2 , moment is kgm2/s . so 5 is given as velocity.

3 0
2 years ago
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