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3 years ago

How much wind is needed to blow away a piece of paper and what distance does it need to be to the fan for it to do so?

Physics

1 answer:

amm18123 years ago

5 0

Wind depends on many factors , it depends on the amount of friction , the positioning ..

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What factors in Earth's relationship to the Sun make life on Earth possible?

Mila [183]

The answer is B.

The planet cannot be too hot or too cold it has to be the right distance from its sun to maintain life.

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3 years ago

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A gas is compressed from 600cm3 to 200cm3 at a constant pressure of 450kPa . At the same time, 100J of heat energy is transferre

Paraphin [41]

Answer: 80J

Explanation:

According to the first principle of thermodynamics:

"Energy is not created, nor destroyed, but it is conserved."

Then this priciple (also called Law) relates the work and the transferred heat exchanged in a system through the internal energy $U$ , which is neither created nor destroyed, it is only transformed. So, in this especific case of the compressed gas:

$\Delta U=Q+W$ (1)

Where:

$\Delta U$ is the variation in the internal (thermal) energy of the system (the value we want to find)

$Q=-100J$ is the heat transferred out of the gas (that is why it is negative)

$W$ is the work is done on the gas (as the gas is compressed, the work done on the gas must be considered positive )

On the other hand, the work done on the gas is given by:

$W=-P \Delta V$ (2)

Where:

$P=450kPa=450(10)^{3}Pa$ is the constant pressure of the gas

$\Delta V=V_{f}-V_{i}$ is the variation in volume of the gas

In this case the initial volume is $V_{i}=600{cm}^{3}=600(10)^{-6}m^{3}$ and the final volume is $V_{f}=200{cm}^{3}=200(10)^{-6}m^{3}$ .

This means:

$\Delta V=200(10)^{-6}m^{3}-600(10)^{-6}m^{3}=-400(10)^{-6}m^{3}$ (3)

Substituting (3) in (2):

$W=-450(10)^{3}Pa(-400(10)^{-6}m^{3})$ (4)

$W=180J$ (5)

Substituting (5) in (1):

$\Delta U=-100J+180J$ (6)

Finally:

$\Delta U=80J$ This is the change in thermal energy in the compression process.

8 0

4 years ago

Calculate the percentage increase in speed of the cyclist when the power output changes from 200 W to 300 W.

Rom4ik [11]

Answer:

50%

Explanation:

Given

Initial power = 200W

Final power = 300W

Increment = 300 - 200 = 100W

percentage increase = increment/initial power * 100

percentage increase = 100/200 * 100%

percentage increase = 0.5 * 100

percentage increase = 50%

Hence the percentage increase in speed is 50%

6 0

3 years ago

The river narrows at a rapids from a width of 12 m to a width of only 5.8 m. The depth of the river before the rapids is 2.7 m;

Alisiya [41]

Answer:

7.89 m/s

Explanation:

Given that

Width of the river, b1 = 12 m

Width of the river, b2 = 5.8 m

Depth of the river, d1 = 2.7 m

Depth of the river, d2 = 0.85 m

Speed of the river, v1 = 1.2 m/s

Speed of the river, v2 = ?

Area of the river before the rapid, a1 = 12 * 2.7 = 32.4 m²

Area of the river after the rapid, a2 = 5.8 * 0.85 = 4.93 m²

To solve this question, we use a relation between the speed of the river and the volume of the river. We say,

Area1 * velocity1 = Area2 * velocity2, and when we substitute the values for each other we have

32.4 * 1.2 = 4.93 * v2

38.88 = 4.93v2

v2 = 38.88 / 4.93

v2 = 7.89 m/s

Therefore, the speed of the river after the rapid is 7.89 m/s

6 0

3 years ago

We cannot consider something to be work unless

iren [92.7K]

force applied causes movement of an object in the same direction as the applied force.

5 0

4 years ago

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