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Lady bird [3.3K]

4 years ago

7

A unit of area, often used in measuring land areas, is the "hectare", defined as 104 m2. An open-pit coal mine consumes 72 hecta

res of land, down to a depth of 25 m, each year. What volume of earth, in cubic kilometers, is removed in this time?

1 answer:

lara31 [8.8K]4 years ago

5 0

Answer:

0.018 km³

Explanation:

Area of land

$A=72\times 10^4\ m^2$

D = Depth of land = 25 m

Volume is given by

$V=AD\\\Rightarrow V=72\times 10^4\times 25\\\Rightarrow V=18000000\ m^3$

Converting to cubic kilometers

$1\ m=\dfrac{1}{1000}\ km$

$1\ m^3=\dfrac{1}{1000^3}\ km^3$

$18000000\ m^3=18000000\times \dfrac{1}{1000^3}=0.018\ km^3$

The volume of Earth removed is 0.018 km³

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Speed and direction are the two scientific componets that make up velocity.

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Which of the following accurately describes between distance and displacement

klasskru [66]

Distance is a scalar and displacement is a vector

Explanation:

Distance and displacement are two different quantities. Let's review them in detail:

Distance is a scalar quantity (only a number followed by unit). Distance represents the total length of the path covered by an object during its motion. Therefore, it does not take into account the direction of motion, in its calculation.
Displacement is a vector quantity, so it has a magnitude, a unit and a direction. Displacement is a vector connecting the initial position to the final position of the motion of an object. Therefore, in its calculation, the direction of motion must be taken into account.

Let's see an example in order to understand distance and displacement better.

Imagine a person moving 5 meters forward and then 2 meters backward. In this case:

The distance covered by the man is just the total lenght of the path covered, therefore: 5 + 2 = 7 meters
The displacement of the man is the distance between the initial and final position. Since the man moved 5 m forward and 2 m backward, his final position is 3 meters forward, therefore the displacement is 3 m in the forward direction.

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4 years ago

The specific gravity of a product can be found on the material safety data sheet. how do you know if a product will sink in wate

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3 years ago

1.45 L of 16°C water is placed in a refrigerator. The refrigerator's motor must supply an extra 10.7 W power to chill the water

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Answer:

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In this case, the coefficient of performance of the refrigerator ( $COP$ ), no unit, is equal to the ratio of the heat rate received from the water to the power needed to work, that is:

$COP = \frac{\dot Q_{L}}{\dot W}$ (1)

$COP = \frac{\rho\cdot V\cdot c_{w}\cdot \Delta T}{\dot W \cdot \Delta t}$ (2)

Where:

$\dot Q_{L}$ - Heat rate received from the water, in watts.

$\dot W$ - Power, in watts.

$\rho$ - Density of water, in kilograms per cubic meter.

$V$ - Volume of water, in cubic meters.

$c_{w}$ - Specific heat of water, in joules per kilogram-degree Celsius.

$\Delta T$ - Temperature change, in degrees Celsius.

$\Delta t$ - Cooling time, in seconds.

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