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Varvara68 [4.7K]
3 years ago
13

Oil at 150 C flows slowly through a long, thin-walled pipe of 30-mm inner diameter. The pipe is suspended in a room for which th

e air temperature is 20 C and the convection coefficient at the outer tube surface is 11 W/m2 K. Estimate the heat loss per unit length of tube.
Physics
1 answer:
chubhunter [2.5K]3 years ago
4 0

Answer:

<em>1.01 W/m</em>

Explanation:

diameter of the pipe d = 30 mm = 0.03 m

radius of the pipe r = d/2 = 0.015 m

external air temperature Ta = 20 °C

temperature of pipe wall Tw = 150 °C

convection coefficient at outer tube surface h = 11 W/m^2-K

From the above,<em> we assumed that the pipe wall and the oil are in thermal equilibrium</em>.

area of the pipe per unit length A = \pi r ^{2} = 7.069*10^{-4} m^2/m

convectional heat loss Q = Ah(Tw - Ta)

Q = 7.069 x 10^-4 x 11 x (150 - 20)

Q = 7.069 x 10^-4 x 11 x 130 = <em>1.01 W/m</em>

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Verdich [7]

Answer:

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Hope this Helps!!!

7 0
3 years ago
A book is sitting on the dashboard of a car that is stopped at a traffic light as the car starts to move forward the book slides
Zina [86]

Answer:

The book remained in its state of rest before the car started to move forward as no direct force acted on it.

Explanation:

According to Newton's first law of motion, a body will continue in its present state of rest, or if it is in motion, will continue to move with uniform speed in a straight line unless aced upon by an external force. This tendency of a body to remain in its state of reset or uniform motion in a straight line is known as inertia and is directly proportional to the mass of the body. The more massive a body, the more inertia it possesses. Thus Newton's first law is also known as the law of inertia.

Considering the case of the book on the dashboard of a stationary car which suddenly starts to move. While the car is stopped at the traffic light, the dashboard where the book sits and the book are both at rest. When the car begins to move forward, the dashboard moves forward with it. However as the book is not a part of the car, no force is directly acting on it, so the book so it stays at rest due to its inertia.

Therefore, as the car is moving forward, the stationary book appears to move backward from the reference point of the car, sliding off the dashboard.

3 0
2 years ago
Kevin decides to soup up his car by replacing the car's wheels with ones that have 1.4 times the diameter of the original wheels
True [87]

Answer:

No.

Explanation:

Given that Kevin decides to soup up his car by replacing the car's wheels with ones that have 1.4 times the diameter of the original wheels. Note that the speedometer in a car is calibrated based on the tire's diameter and on the distance the tire covers in each revolution. (a) Will the reading of the speedometer change ?

Considering the formula

V = wr

Where

V = linear speed

W = angular speed

r = radius of the wheel.

But W = 2πrf

Where the the 2 and pi are constant. The radius of the first wheel will be small but counter balance with the larger frequency.

While the radius of the second wheel may be large but it will be of a small frequency.

We can therefore conclude that the reading on the speedometer will not change. Because speedometer will read the linear speed V.

7 0
2 years ago
motorcycle accelerates from rest to a final velocity of 27 m/s in 9 seconds. What is its acceleration?
Vedmedyk [2.9K]

Answer:

3 m/s squared

Explanation:

The formula you use is Vf= Vi + at. You rearrange it to a= Vf - Vi/t. The Vf is 27m/s. The Vi is 0m/s and the t is 9s. Cross out Vi since it’s zero and you’re left with a= 27m/s divided by 9s, which equals 3

5 0
2 years ago
A closely wound search coil has an area of 3.13 cm2, 135 turns, and a resistance of 61.1 Ω. It is connected to a charge-measurin
erastovalidia [21]

Answer:

Explanation:

Let the magnitude of magnetic field be B .

flux passing through the coil's  = area of coil x field x no of turns

Φ = 3.13 x 10⁻⁴ x B x 135 = 422.55 x 10⁻⁴ B .

emf induced = dΦ / dt , Φ is magnetic flux.

current i = dΦ /dt x 1/R

charge through the coil = ∫ i dt

= ∫   dΦ /dt x 1/R dt

= 1 / R ∫ dΦ

= Φ / R

Total resistance R = 61.1 + 44.4 = 105.5 ohm .

3.44 x 10⁻⁵ = 422.55 x 10⁻⁴ B / 105.5

B = 3.44 x 10⁻⁵ x 105.5  / 422.55 x 10⁻⁴

= .86 x 10⁻¹

= .086 T .

8 0
2 years ago
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