PHYSICS COLLEGE

An inventor claims to have developed a power cycle having a thermal efficiency of 40%, while operating between hot and cold reservoirs at temperature th and tc 5 300 k, respectively, where th is (a) 900 k, (b) 500 k, (c) 375 k. evaluate the claim for each case

Answers

Answer 1

Answer:

From Carnot's theorem, for any engine working between these two temperatures:

efficiency <= (1-tc/th) * 100

Given: tc = 300k (from question assuming it is not 5300 as it seems)

For a, th = 900k, efficiency = (1-300/900) = 70%

For b, th = 500k, efficiency = (1-300/500) = 40%

For c, th = 375k, efficiency = (1-300/375) = 20%

Hence in case of a and b, efficiency claimed is lesser than efficiency calculated, which is valid case and in case of c, however efficiency claimed is greater which is invalid.

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Explain how ultrasound devices use the Doppler effect to create images of body parts. HELP ME ASAP!! Will give brainliest answer!!

Answers

Answer:

Transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe. The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).

Explanation:

Doppler ultrasound works by measuring sound waves that are reflected from moving objects, such as red blood cells.

Answer:

The guy above is pretty good

Explanation:

I'd go with that answer, give them brainliest

If the speed of light in a medium is 2 x 10^8 m/s, the medium's index of refraction is?

Answers

speed of light in the air is 3 x 10^8
so index of refractions would be speed of light divided by speed in the medium
3/2 = 1.5

Answer: n=1.5

by the way it is glass :)

A rock is thrown vertically upward from some height above the ground. It rises to some maximum height and falls back to the ground. What one of the following statements is true if air resistance is neglected? The acceleration of the rock is zero when it is at the highest point. The speed of the rock is negative while it falls toward the ground. As the rock rises, its acceleration vector points upward. At the highest point the velocity is zero, the acceleration is directed downward. The velocity and acceleration of the rock always point in the same direction.

Answers

Answer:

At the highest point the velocity is zero, the acceleration is directed downward.

Explanation:

This is a free-fall problem, in the case of something being thrown or dropped, the acceleration is equal to -gravity, so -9.80m/s^2. So, the acceleration is never 0 here.

I attached an image from my lecture today, I find it to be helpful. You can see that because of gravity the acceleration is pulled downwards.

At the highest point the velocity is 0, but it's changing direction and that's why there's still an acceleration there.

A commercial aircraft is flying westbound east of the Sierra Nevada Mountains in California. The pilot observes billow clouds near the same altitude as the aircraft to the south, and immediately turns on the "fasten seat belt" sign. Explain why the aircraft experiences an abrupt loss of 500 meters of altitude a short time later.

Answers

Answer:

Billow clouds provide a visible signal to aviation interests of potentially dangerous turbulent sky since they indicate instability in air currents.

Explanation:

Billow clouds are created in regions that are not stable in a meteorological sense. They are frequently present in places with air flows, and have marked vertical shear and weak thermal separation and inversion (colder air stays on top of warmer air). Billow clouds are formed when two air currents of varying speeds meet in the atmosphere. They create a stunning sight that looks like rolling ocean waves. Billow clouds have a very short life span of minutes but they provide a visible signal to aviation interests of potentially dangerous turbulent sky since they indicate instability in air currents, which although may not affect us on the ground but is a concern to aircraft pilots. The turbulence due to the Billow wave is the only logical explanation for the loss of 500 m in altitude of the plane.

The production of heat by metabolic processes takes place throughout the volume of an animal, but loss of heat takes place only at the surface (i.e. the skin). Since heat loss must be balanced by heat production if an animal is to maintain a constant internal temperature, the relationship between surface area and volume is relevant for physiology. If the surface area of a cube is increased by a factor of 2, by what factor does the volume of the cube change? Give your answer to two significant figures. 1.59

Answers

To solve this problem we will apply the concepts related to the change in length in proportion to the area and volume. We will define the states of the lengths in their final and initial state and later with the given relationship, we will extrapolate these measures to the area and volume

The initial measures,

$\text{Initial Length} = L$

$\text{Initial surface Area} = 6L^2$ (Surface of a Cube)

$\text{Initial Volume} = L^3$

The final measures

$\text{Final Length} = L_f$

$\text{Final surface area} = 6L_f^2$

$\text{Final Volume} = L_f^3$

Given,

$((SA)_f)/((SA)_i) = 2$

Now applying the same relation we have that

$((L_f)/(L_i))^2 = 2$

$(L_f)/(L_i) = √(2)$

The relation with volume would be

$((Volume)_f)/((Volume)_i) = ((L_f)/(L_i))^3$

$((Volume)_f)/((Volume)_i) = (√(2))^3$

$((Volume)_f)/((Volume)_i) = (2√(2))$

$((Volume)_f)/((Volume)_i) = 2.83$

Volume of the cube change by a factor of 2.83

A pressure antinode in a sound wave is a region of high pressure, while a pressure node is a region of low pressure.True
False

Answers

A pressure antinode in a sound wave is not a region of high pressure, while a pressure node is not a region of low pressure.

The answer is false

Final answer:

A pressure antinode in a sound wave is indeed a region of high pressure, while a pressure node is a region of low pressure. These definitions hold true for all types of waves.

Explanation:

That's true. In terms of sound waves, a pressure antinode is a region of high pressure, while a pressure node is a region of low pressure. This is true for all types of waves, not only sound waves. In essence, a wave moves through a medium (in case of a sound wave, that medium is typically air) by creating areas of high and low pressure - the high pressure areas are called antinodes, and the low pressure areas are called nodes.

Learn more about Sound Waves here:

brainly.com/question/31375531

#SPJ2

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