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3 years ago

Which of the following is a chemical change?

1 answer:

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a). Water is still H₂O after it freezes.

b). Ice is still H₂O after it melts.

c). Wire is still Cu when it's bent.

d). Paper combines with the O₂ in the air, and turns into
a lot of new compounds when it burns.

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A submarine sends a signal and receives an echo after 5 seconds. Calculate the speed of sound if distance of object from submari

Reil [10]

$speed = distance \div time$
Since the sound travels from the submarine to the object AND back, it actually travelled 3625x2=7250m.

$7250 \div 5 = 1450$
Speed of sound: 1450m/s

3 0

3 years ago

Read 2 more answers

The acceleration due to gravity near Earth ... Select one: a. varies inversely with the distance from the center of Earth. by. v

vladimir1956 [14]

Answer:

b. varies inversely with the square of the distance from the center of Earth.

Explanation:

Comparing the Newton's law of universal gravitation and second law of motion;

from Newton's second law of motion,

F = ma ............. 1

from New ton's law of universal gravitation,

F = $\frac{GMm}{r^{2} }$ ........... 2

Equating 1 and 2, we have;

mg = $\frac{GMm}{r^{2} }$

g = $\frac{GM}{r^{2} }$

Therefore, the acceleration due to gravity near Earth, g, is inversely proportional to the square of the distance from the center of Earth.

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3 years ago

What kind of proof is required when disproving old ideas?

GrogVix [38]

Answer:

Explanation:

In order to disprove an old theory you need to prove a new one that contradicts it using scientific research and experimentation

8 0

3 years ago

The mass of a coin is measured to be 12.5±0.1 g. The diameter is 2.8±0.1 cm and the thickness 2.1 ±0.1 mm. Calculate the average

Evgesh-ka [11]

The average density of the material from which the coin is made is 9.67 g/cm³.

<h3>Volume of the coin</h3>

The volume of the coin at the given diameter is calculated as follows;

V = Ah

where;

A is area of the coin
h is the thickness of the coin

V = πd²/4 x h

V = π(2.8)²/4 x (0.21 cm)

V = 1.293 cm³

<h3>average density of the coin</h3>

The average density of the material from which the coin is made is calculated as follows;

density = mass/volume

density = 12.5 g / (1.293 cm³)

density = 9.67 g/cm³

Thus, the average density of the material from which the coin is made is 9.67 g/cm³.

Learn more about average density here: brainly.com/question/1354972

#SPJ1

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2 years ago

The frequency of a certain sound is 440 Mz. What is the wavelength of this sound when the temperature of the air is (a) 20°C; (b

Serggg [28]

Answer:

Explanation:

We know the frequency and the velocity, both of which have good units. All we have to do is rearrange the equation and solve for

Let's plug in our given values and see what we get!

340

440

−

0.773

3 0

2 years ago