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4 years ago

Sound travels slow in cold air. Why does the speed of sound depend on air temperature?

1 answer:

3 0

Heat is like sound, both are a form of kinetic energy. Molecules vibrate faster when at higher temps. since molecules vibrate faster, sound waves travel quicker <span />

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A sample of oxygen gas at 25.0Â°c has its pressure tripled while its volume is halved. What is the final temperature of the gas?

Marat540 [252]

Answer:

447 K

Explanation:

25 C = 25 + 273 = 298 K

Assuming ideal gas, we can apply the ideal gas law

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

$T_2 = T_1\frac{P_2}{P_1}\frac{V_2}{V_1}$

Since pressure is tripled, then $P_2 / P_1 = 3$ . Volume is halved, then $V_2 / V_1 = 0.5$

$T_2 = 298*3*0.5 = 447 K$

4 0

3 years ago

Read 2 more answers

NASA is giving serious consideration to the concept of solar sailing. A solar sailcraft uses a large, lowmass sail and the energ

Elan Coil [88]

Answer:

a) the reflective surface has twice the energy transfer

b) A = 1.3 10²⁷ km²

c) the energy emitted by the sun is distributed in a sphere that depends on the square of the distance, and the gravitational force depends on the square of the distance

Explanation:

a) The pressure exerted on the candle is related to the variation of the momentum

P = $\frac{1}{c} \ \frac{dp}{dt}$

in a case of absorption (inelastic shock) all the energy is absorbed therefore the pressure is

P = \frac{1}{c} \ \frac{dp}{dt}

in the case of reflection (elastic shock) an energy is absorbed by absorbing the light and then by action and reaction the same energy is absorbed in the reflected light

P = 2 \frac{1}{c} \ \frac{dp}{dt}

In conclusion, the reflective surface has twice the energy transfer.

b) pressure is defined with force per unit area

P = F / A

F = P A

this force must be greater than the gravitational force of attraction of the sun

Fg = G m Ms / r²

let's look for the case that the two forces are equal

F = Fg

P A_sail = G m Ms = r²

suppose a fully reflective sail

$2 \frac{S}{c} \ A_{sail} = G \frac{m M_s}{r^2}$

The pointing vector is the power delivered per unit area

S = I = P / A

where A is the area of the sphere where the is distributed by the sun

A = 4π r²

we substitute

$\frac{2P}{c} \ \frac{A_{sail}}{4 \pi r^2} = G \frac{m M_s}{r^2}$

$\frac{1}{2 \pi \ c }$ A_{sail} = G m M_s

A = G m M_s 2π c

let's calculate

A = 6.67 10⁻¹¹ 10000 2 10³⁰ 2π 3 10⁸

A = 1,257 10³³ m²

let's reduce to km²

A = 1.3 10³³ m² (1km / 10³ m) ²

A = 1.3 10²⁷ km²

c) The size of the candle is independent of the distance to the sun because the energy emitted by the sun is distributed in a sphere that depends on the square of the distance, and the gravitational force depends on the square of the distance, therefore the two dependencies are canceled.

8 0

3 years ago

Light in vacuum is incident on the surface of a glass slab. In the vacuum the beam makes an angle of 38.0° with the normal to th

iren [92.7K]

Answer:

n_glass = 1.404

Explanation:

In order to calculate the index of refraction of the light you use the Snell's law, which is given by the following formula:

$n_1sin\theta_1=n_2sin\theta_2$ (1)