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Yanka [14]
3 years ago
10

what is the efficiency of an engine that dies 288 J of work and exhausts 72 J of heat while taking 360 J of heat?

Physics
1 answer:
Yuliya22 [10]3 years ago
5 0

Answer:

80%

Explanation:

Energy Input: 360 J

Energy Output: 288 J

e= 288/360 × 100

e= 80%

Alternatively,

e= W(total)/ Q (in)

e= 288/360

e=0.8×100

e=80%

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Assume that the physics instructor would like to have normal visual acuity from 21 cm out to infinity and that his bifocals rest
shutvik [7]

This is note the complete question, the complete question is:

One of the lousy things about getting old (prepare yourself!) is that you can be both near-sighted and farsighted at once. Some original defect in the lens of your eye may cause you to only be able to focus on some objects a limited distance away (near-sighted). At the same time, as you age, the lens of your eye becomes more rigid and less able to change its shape. This will stop you from being able to focus on objects that are too close to your eye (far-sighted). Correcting both of these problems at once can be done by using bi-focals, or by placing two lenses in the same set of frames. An old physicist instructor can only focus on objects that lie at distance between 0.47 meters and 5.4 meters.

Assume that the physics instructor would like to have normal visual acuity from 21 cm out to infinity and that his bifocals rest 2.0 cm from his eye. What is the refractive power of the portion of the lense that will correct the instructors nearsightedness?

Answer:  3.04 D

Explanation:

when an object is held 21 cm away from the instructor's eyes, the spectacle lens must produce 0.47m ( the near point) away.

An image of 0.47m from the eye will be ( 47 - 2 )

i.e 45 cm from the spectacle lens since the spectacle lens is 2cm away from the eye.

Also, the image distance will become negative

gap between lense and eye = 2cm

Therefore;

image distance d₁ = - 45cm = - 0.45m

object distance  d₀ = 21 - 2 = 19cm = 0.19m

P = 1/f = 1/ d = 1/d₀ + 1/d₁ = 1/0.19 + (-1/0.45)

P = 1/f =  5.26315789 - 2.22222222

P = 1/f = 3.04093567 ≈ 3.04 D

5 0
3 years ago
A measurement must include both a number and a(an)
IrinaK [193]
<span>A measurement must include both a number and an unit of measurement. </span>
7 0
2 years ago
When a wave strikes a solid barrier it behaves like a basketball hitting a backboard this wave behavior years called?
Mama L [17]
This behavior is called reflection.
Reflection is a change of in direction of the wave when it reaches another medium. Imagine a wave colliding with a glass in a tank of water.
During reflection, some of the initial energy of the wave is lost.
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3 years ago
Ballon volume of 3200ml of xenon gas is at a gauge pressure of 122kPa and a temperature of 27c. What is the volume when the ball
N76 [4]

Given:

The initial volume of the gas, V₁=3200 ml=3.2×10⁻³ m³

The initial pressure of the gas, P₁=122 kPa

The initial temperature of the gas, T₁=27 °C=300 K

The final temperature, T₂=65 °C=338 K

The final pressure, P₂=112 kPa

To find:

The final volume of xenon gas.

Explanation:

From the combined gas law,

\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}

Where V₂ is the volume after it is heated.

On rearranging the above equation,

V_2=\frac{T_2P_1V_1}{T_1P_2}

On substituting the known values,

\begin{gathered} V_2=\frac{338\times112\times10^3\times3.2\times10^{-3}}{300\times112\times10^3} \\ =3.61\text{ m}^3 \end{gathered}

Final answer:

The volume of the balloon when it is heated is 3.61 m³

4 0
1 year ago
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Irina-Kira [14]
Mass= is how big something is.
Weight= is how heavy something is.
They are different things because weight is talking about heavy... not how big it is.
5 0
2 years ago
Read 2 more answers
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