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Helga [31]
3 years ago
6

A street light is mounted at the top of a 15-ft-tall pole. a man 6 ft tall walks away from the pole with a speed of 4 ft/s along

a straight path. how fast is the tip of his shadow moving when he is 30 ft from the pole?

Physics
1 answer:
Arlecino [84]3 years ago
5 0

Answer: 2.67 ft/s



Explanation:



1) The diagram with the triangle that represents the situation is in the image attached.


2) Similarity properties


(x + y) / 15 = y/6


⇒ 6(x+y) = 15y


⇒ 6x + 6y = 15y


⇒ 6x = 15y - 6y


⇒ 6x = 9y


⇒ y = 6x / 9


⇒ y = 2x / 3


3) Velocity is the derivative respecto to time. Then, find the derivative respect to time, t, on both sides


dy/dt = (2/3)dx/dt


4) The statement tells v = dx/dt = 4 ft/s


⇒ dy/dt = (2/3) 4 ft/s = (8/3)m/s ≈ 2.67 ft/s


Notice that this speed is constant, it does not depends upon the distance of 30 ft.

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Answer:

acidic colorless gas

Explanation:

Carbon dioxide is an acidic colorless gas with a density of about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth's atmosphere as a trace gas.

4 0
3 years ago
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One speaker generates sound waves with amplitude A.
raketka [301]

Answer:

iv) It is 9x bigger than before

Explanation:

As the amplitudes of the new speakers add directly with the original one, taking into account the phase that they have, the composed amplitude of the sound wave is as follows:

At = A + 4A -2A = 3 A

The intensity of the wave, assuming it propagates evenly in all directions, is constant at a given distance from the source, and can be expressed as follows:

I = P/A

where P= Power of the wave source, A= Area (for a point source, is equal to the surface area of a sphere of radius r, where is r is the distance to the source along a straight line)

For a sinusoidal wave, the power is proportional to the square of the amplitude, so the intensity is proportional to the square of the amplitude also.

If the amplitude changes increasing three times, the change in intensity will be proportional to the square of the change in amplitude, i.e., it will be 9 times bigger.

So, the statement iv) is the right one.

7 0
3 years ago
Find the ratio of the diameter of iron to copper wire, if they have the same resistance per unit length (as they might in househ
Natasha_Volkova [10]

Answer:

The ratio of the diameter of iron to Cu is;

\frac{d{Fe}   }{ d{Cu}   } =\sqrt{\frac{p_{Fe} }{ p_{Cu} }}

Explanation:

R=(ρL)/A

  • R is resistance,
  • L is length,
  • A is area,
  • ρ is resistivity
  • d is diameter

from the question the two materials have the same resistance per unit length.

\frac{R}{L}= \frac{p}{A}

\frac{R}{L}   for iron = \frac{R}{L}  for copper

This means we can equate ρ/A for both materials.

\frac{p_{Fe} }{A_{Fe} } =\frac{p_{Cu} }{A_{Cu} }

re-arranging the equation we have,

\frac{A_{Fe}}{A_{Cu} } =\frac{p_{Fe} }{ p_{Cu} }

A=\pi \frac{d^{2} }{4}

\frac{A_{Fe}}{A_{Cu} } =\frac{d^{2}{Fe}   }{ d^{2}{Cu}   }

\frac{d^{2}{Fe}   }{ d^{2}{Cu}   } =\frac{p_{Fe} }{ p_{Cu} }

\frac{d{Fe}   }{ d{Cu}   } =\sqrt{\frac{p_{Fe} }{ p_{Cu} }}

5 0
3 years ago
Boron (B) has an atomic number of 5 and an atomic mass of 11. Boron has _____.
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Answer:

the answer is 5 electrons

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6 0
3 years ago
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a ball is thrown striaght up in the air and then falls back to earth. if the downward fall takes 2.2s, how fast is the ball trav
lapo4ka [179]

The velocity of the ball when it strikes the ground, given the data is 21.56 m/s

<h3>Data obtained from the question</h3>

From the question given above, the following data were obtained:

  • Time to reach ground from maximum height (t) = 2.2 s
  • Initial velocity (u) = 0 m/s
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<h3>How to determine the velocity when the ball strikes the ground</h3>

The velocity of the ball when it strikes the ground can be obtained as illustrated below:

v = u + gt

v = 0 + (9.8 × 2.2)

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v = 21.56 m/s

Thus, the velocity of the ball when it strikes the ground is 21.56 m/s

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