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3 years ago

Help me please asap :(

Physics

1 answer:

mixer [17]3 years ago

8 0

17. a
18. c
19. a
20. c
21. c

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A substance that accelerates the rate of a chemical reaction is called a(an)

Dahasolnce [82]

<span>A substance that accelerates the rate of chemical reaction is called a catalyst. It serves as an alternative pathway for the reaction product. The increase of rate of chemical reaction is because catalyst has low activiation energy than the original pathway. The low activation energy will increase the amount of molecules that can benefit in the energy created by the catalyst.</span>

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3 years ago

Which one of the following temperatures (in °C) is equivalent to 294 K?

vaieri [72.5K]

Answer:

Explanation: its actually 20.85 but i guess they round to 21

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3 years ago

What is thermodynamics?

Kryger [21]

D. The flow of energy,heat, and work

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2 years ago

One of the dangers of tornados and hurricanes is the rapid drop in air pressure that is associated with such storms. Assume that

Rufina [12.5K]

Answer:

45930.52N

Explanation:

Net force = (internal pressure - external pressure)× area of window

Net force = (1.02 - 0.910)atm × 2.03m × 2.03m = 0.11atm × 4.1209m^2 = 0.11 × 101325N/m^2 × 4.1209m^2 = 45930.52N

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3 years ago

Telephone signals are often transmitted over long distances by microwaves. What is the frequency of microwave radiation with a w

amm1812

Answer:

1) f= 8.6 GHz

2) t= 0.2 ms

Explanation:

Since microwaves are electromagnetic waves, they move at the same speed as the light in vacuum, i.e. 3*10⁸ m/s.
There exists a fixed relationship between the frequency (f) , the wavelength (λ) and the propagation speed in any wave, as follows:

$v = \lambda * f (1)$

Replacing by the givens, and solving for f, we get:

$f =\frac{c}{\lambda} =\frac{3e8m/s}{0.035m} = 8.57e9 Hz (2)$

⇒ f = 8.6 Ghz (with two significative figures)

Assuming that the microwaves travel at a constant speed in a straight line (behaving like rays) , we can apply the definition of average velocity, as follows:

$v =\frac{d}{t} (3)$

where v= c= speed of light in vacuum = 3*10⁸ m/s

d= distance between mountaintops = 52 km = 52*10³ m

Solving for t, we get:

$t = \frac{d}{c} = \frac{52e3m}{3e8m/s} = 17.3e-5 sec = 0.173e-3 sec = 0.173 ms (4)$

⇒ t = 0.2 ms (with two significative figures)

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3 years ago