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xenn [34]
3 years ago
9

Which statement describes a question that can be answered by a scientific

Physics
1 answer:
alex41 [277]3 years ago
6 0

Answer: b

Explanation:

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If you wanted to increase the gravitational force between two objects what would you do
adelina 88 [10]
Double the force on the object
6 0
4 years ago
Read 2 more answers
Bearing in mind that a sound reflects off an object if the object is larger than the wavelength of the sound, calculate the wave
grandymaker [24]

Answer:

mucilage can detect objects the size of millimeters, whereas humans can only detect objects larger than centimeters

Explanation:

The human ear can detect sound in the range of 20 to 20000hz, we are asked to find the mid-range wavelength of the ear at f = 10000 Hz

let's use the relationship between wave speed, wavelength and frequency

           v = λ f

           λ= v / f

           λ = 343/10000

           λ = 3.43 10⁻² m

the sound range of a bat is between 25 10³ Hz and 100 10³ Hz, they also ask for the wavelength in the middle range

         

          f = (100 10³ + 25 10³) / 2

          f = 62.5 10³ Hz

          λ = 343 / 62.5 10³

          λ = 5.5 10⁻³ m

Therefore the size of the object that a bat can detect is much smaller than the size that a human can detect, therefore the bat is capable of detecting insects, but humans.

The mucilage can detect objects the size of millimeters, whereas humans can only detect objects larger than centimeters

4 0
3 years ago
A 55.6-kg skateboarder starts out with a speed of 2.44 m/s. He does 80.4 J of work on himself by pushing with his feet against t
Vikentia [17]

(a) -1620.8 J

The initial kinetic energy of the  skateboarder is:

K_i = \frac{1}{2}mu^2 = \frac{1}{2}(55.6 kg)(2.44 m/s)^2=165.5 J

where m is the skateboarder's mass and u his initial speed;

While the final kinetic energy is

K_f = \frac{1}{2}mv^2 = \frac{1}{2}(55.6 kg)(7.24 m/s)^2=1457.2 J

where v is his final speed.

So the change in kinetic energy is

\Delta K=K_f - K_i = 1457.2 J -165.6 J = 1291.6 J

According to the work-energy theorem, the change in mechanical energy (kinetic+potential) of the skateboarder is equal to the work done on it:

\Delta K + \Delta E_p = W + W_f

where

W = 80.4 J is the work done by the skateboarder on himself

W_f = -244 J is the work done by friction

\Delta E_p = E_p_f - E_p_i is the change in gravitational potential energy

Solving for \Delta E_p,

\Delta E_p = W+W_f - \Delta K=80.4 J - 244 J - 1457.2 J = -1620.8 J

(b) 2.97 m

The change in potential energy of the skateboarder can be written as

\Delta E_p = mg \Delta h

where

m = 55.6 kg is the mass

g = 9.8 m/s^2 is the acceleration of gravity

\Delta h is the change in vertical height of the skateboarder

Solving for \Delta h,

\Delta h = \frac{\Delta E_p}{mg}=\frac{-1620.8 J}{(55.6 kg)(9.8 m/s^2)}=-2.97 m

Where the negative sign means the skateboarder has moved downwards. Since we are interested only in the absolute value, the answer is

h = 2.97 m

7 0
3 years ago
A plumber is trying to fix a clog in a vertical pipe, but does not know how far down in the pipe the clog and the water level is
PIT_PIT [208]

Answer:

the shortest distance to the obstruction is 0.431 m

Explanation:

We can see this system as an air column, where the plumber is open and where the water is closed, in the case when he hears the sound there is a phenomenon of resonance and superposition of waves with constructive interference.

For the lowest resonance we must have a node where the water is and a maximum where the plumber is a quarter of the wavelength

       λ = ¼ L

If we are in a major resonance specifically the following resonance. We have a full wavelength plus a quarter of the wavelength

    λ = 4L / 3

The general formula is

    λ = 4L / n            n = 1, 3, 5, 7,…

In addition the wave speed is the product of the frequency by the wavelength

    v = λ f

Let's replace

    v = (4L / n) f

    L = v n / (4 f)

Now we can calculate the depth or length of the air column

If we have the first standing wave n = 1

    L = 340 1 / (4 197)

    L = 0.431 m

If it is the second resonance n = 3

    L = 340 3 / (4 197)

    L = 1.29 m

We can see the shortest distance to the obstruction is 0.431 m

5 0
3 years ago
Chứng minh mặt trời là nguồn gốc của tất cả nguồn năng lượng
Hatshy [7]

An Excerpt from “Optimism”

by Helen Keller

1 Could we choose our environment, and were desire in human undertakings synonymous with

endowment, all men would, I suppose, be optimists. Certainly most of us regard happiness as

the proper end of all earthly enterprise. The will to be happy animates alike the philosopher, the

prince and the chimney-sweep. No matter how dull, or how mean, or how wise a man is, he feels

that happiness is his indisputable right.

2 It is curious to observe what different ideals of happiness people cherish, and in what singular

places they look for this well-spring of their life. Many look for it in the hoarding of riches, some

in the pride of power, and others in the achievements of art and literature; a few seek it in the

exploration of their own minds, or in the search for knowledge.

3 Most people measure their happiness in terms of physical pleasure and material possession.

Could they win some visible goal which they have set on the horizon, how happy they would be!

Lacking this gift or that circumstance, they would be miserable. If happiness is to be so

measured, I who cannot hear or see have every reason to sit in a corner with folded hands and

weep. If I am happy in spite of my deprivations, if my happiness is so deep that it is a faith, so

thoughtful that it becomes a philosophy of life,—if, in short, I am an optimist, my testimony to

the creed of optimism is worth hearing....

4 Once I knew the depth where no hope was, and darkness lay on the face of all things. Then

love came and set my soul free. Once I knew only darkness and stillness. Now I know hope and

joy. Once I fretted and beat myself against the wall that shut me in. Now I rejoice in the

consciousness that I can think, act and attain heaven. My life was without past or future; death,

the pessimist would say, “a consummation devoutly to be wished.” But a little word from the

fingers of another fell into my hand that clutched at emptiness, and my heart leaped to the

rapture of living. Night fled before the day of thought, and love and joy and hope came up in a

passion of obedience to knowledge. Can anyone who has escaped such captivity, who has felt

the thrill and glory of freedom, be a pessimist?

5 My early experience was thus a leap from bad to good. If I tried, I could not check the

momentum of my first leap out of the dark; to move breast forward is a habit learned suddenly

at that first moment of release and rush into the light. With the first word I used intelligently, I

learned to live, to think, to hope. Darkness cannot shut me in again. I have had a glimpse of the

shore, and can now live by the hope of reaching it.

6 So my optimism is no mild and unreasoning satisfaction. A poet once said I must be happy

because I did not see the bare, cold present, but lived in a beautiful dream. I do live in a

beautiful dream; but that dream is the actual, the present,—not cold, but warm; not bare, but

furnished with a thousand blessings. The very evil which the poet supposed would be a cruel

6) Read the last sentence from the text.

Only by contact with evil could I have learned to feel by contrast the beauty of truth and love and goodness.

Explain how Helen Keller develops this idea in the text. Use specific details to

support your answer.

8 0
3 years ago
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