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3 years ago

The air in your classroom has

Physics

1 answer:

mel-nik [20]3 years ago

8 0

D.) all of the above

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When are magnets attracted and when are they repelled.

vova2212 [387]

Magnets are attracted when each of the different sides, most commonly known as "North" and "South", are facing each other. They repel when North and North, or South and South are facing each other.

3 0

3 years ago

A train is moving in a straight railway where it covered one third of the distance with

Alexxandr [17]

Answer:

<em>The average speed of the train is 45 km/h</em>

Explanation:

<u>Speed</u>

It's defined as the distance (d) per unit of time (t) traveled by an object. The formula is:

$\displaystyle v=\frac{d}{t}$

Let's call x the total distance covered by the train. It covered d1=1/3x with a speed of v1=25 km/h. The time taken is calculated solving for t:

$\displaystyle t_1=\frac{d_1}{v_1}$

$\displaystyle t_1=\frac{1/3x}{25}$

$\displaystyle t_1=\frac{x}{75}$

Now the rest of the distance:

d2 = x - 1/3x = 2/3x

Was covered at v2=75 km/h. Thus the time taken is:

$\displaystyle t_2=\frac{d_2}{v_2}$

$\displaystyle t_2=\frac{2/3x}{75}$

$\displaystyle t_2=\frac{2x}{225}$

The total time is:

$\displaystyle t_t=\frac{x}{75}+\frac{2x}{225}$

$\displaystyle t_t=\frac{3x}{225}+\frac{2x}{225}$

$\displaystyle t_t=\frac{5x}{225}$

Simplifying:

$\displaystyle t_t=\frac{x}{45}$

The average speed is the total distance divided by the total time:

$\displaystyle \bar v=\frac{x}{\frac{x}{45}}$

Simplifying:

$\boxed{\displaystyle \bar v=45\ km/h}$

The average speed of the train is 45 km/h

5 0

3 years ago

The distance from one crest to the next is the ________.

nikitadnepr [17]

Answer:

Wavelength.

Explanation:

1 period, or wavelength, is measured from one crest to another or from one trough to another.

7 0

3 years ago

7. The energy source used to produce most of the electrical energy in the United States is ____________________.

Fudgin [204]

Fossil fuels like coal, natural gas and oil.

Hopes this helps!

4 0

3 years ago

Read 2 more answers

If air resistance acts on a falling object will all of its potential energy be converted into kinetic energy?

Mademuasel [1]

Answer:

No, some energy will be dissipated energy due to work of air resistance.

6 0

2 years ago