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2 years ago

Which of these cultures did NOT make major contributions to astronomy?

1 answer:

6 0

I can't particularly place what Icelandic contributed.

But every other culture contributed majorly.

So I would go for option b.

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Why does the sample on a microscope slide need to be very thin?

ziro4ka [17]

B. so light can shine through it from below.

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3 years ago

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The amount of energy which is transported past a given area of the medium per unit of time is known as the ________ of the sound

Aliun [14]

The term that describes the amount of energy transported past a given area of the medium per unit time would be "intensity." In addition, the formula for computing intensity would be:

Intensity = Energy / (Time * Area)

It can be implied that the wave would be more intense when its energy transfer rate gets increased and vibration amplitudes also increases.

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2 years ago

What is the magnitude of the applied electric field inside an aluminum wire of radius 1.2 mm that carries a 3.0-a current? [ σal

galben [10]

Hello

1) First of all, since we know the radius of the wire ( $r=1.2~mm=0.0012~m$ ), we can calculate its cross-sectional area
$A=\pi r^2 = 3.14 \cdot (0.0012~m)^2=4.5\cdot10^{-6}~m^2$

2) Then, we can calculate the current density J inside the wire. Since we know the current, $I=3~A$ , and the area calculated at the previous step, we have
$J= \frac{I}{A}= \frac{3~A}{4.5\cdot10^{-6}~m^2} = 6.63\cdot10^5 ~A/m^2$

3) Finally, we can calculate the electric field E applied to the wire. Given the conductivity $\sigma=3.6\cdot10^7~ \frac{A}{Vm}$ of the aluminium, the electric field is given by
$E= \frac{J}{\sigma}= \frac{ 6.63\cdot10^5 ~A/m^2}{3.6\cdot10^7~ \frac{A}{Vm} } = 0.018~V/m$

4 0

3 years ago

Explain why pumice floats and why ironwood sinks

almond37 [142]

Answer:

A quick way of describing density is to describe an object as heavy or light for its size. Pumice stone, unlike regular rock, does not sink in water because it has a low density. An ironwood branch is very dense and sinks in water.

Hope that helps. x

6 0

1 year ago

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NASA is giving serious consideration to the concept of solar sailing. A solar sailcraft uses a large, low- mass sail and the ene

RUDIKE [14]

Answer:

d. The sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.

Explanation:

Let us take the momentum of a photon unit as u

we know that the rate of change of momentum is proportional to the force exerted.

For a absorbing surface, the photon is absorbed, therefore the final momentum is zero. From this we can say that

F = (u - 0)/t = u/t

for a unit time, the force is proportional to the momentum of the wave due to its energy density. Therefore,

F = u

For a reflecting surface, the momentum of the wave strikes the sail and changes direction. Since we know that the speed of light does not change, then the force is proportional to

F = (u - (-u))/t = 2u/t

just as the we did above, it becomes

F = 2u.

From this we can see that the force for a reflective sail is twice of that for an absorbing sail, and we know that the pressure is proportional to the force for a given area. From these, we conclude that the sail should be reflective because in this case the momentum transferred to the sail per unit area per unit time is larger than for absorbing sail, therefore the radiation pressure is larger for the reflective sail.

3 0

3 years ago