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Elanso [62]
2 years ago
11

If the radius of a coinis 20cm, find itssurface area -​

Physics
1 answer:
meriva2 years ago
8 0

Answer:

800\picm²

Explanation:

Given parameters:

radius of the coin  = 20cm

Unknown:

Surface area of the coin  = ?

Solution:

A coin is made up of two faces;

  Surface area  = 2(πr²)

Insert the parameters and solve;

     Surface area = 2(\pi  x 20^{2})

    Surface area = 800\picm²

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8. The legs of a young man are each 0.650 meters long. What is his maximum walking speed?
Norma-Jean [14]

Answer:

2.52 m/s

Explanation:

When the man takes a step, his foot is stationary while his body revolves around it.  At the point when his body is directly above his foot, there will be no normal force at his maximum speed.

Sum of the forces in the radial direction:

∑F = ma

mg = m v² / r

g = v² / r

v = √(gr)

Given that r = 0.650 m:

v = √(9.8 m/s² × 0.650 m)

v = 2.52 m/s

8 0
3 years ago
How has the farming industry been affected by the use of fossil fuels?
Mashutka [201]

Fossil fuels have led to an increase in food costs.

Explanation:

Buried organic material over million of years form combustible geologic deposits of organic materials called fossil fuels that can be converted crude oil, natural gas, or coal.

Fossil fuel are currently used as a source of energy in machine and equipment applied in the farming industry. Mechanization has been made possible due to this type of fuel availability thus larger farms have been prepared for cultivation.In addition, other processes such as planting,weeding and harvesting are currently performed by farming machines which are propelled by fossil energy. So in general, fossil fuels in the farming industry has led to increase in amount of crop harvested because more farms are under cultivation and farming process is now mechanized. However, due to use of machines and energy, the production cost has increased, thus to cover for this increased cost, the prices for food products increases, making the cost of food commodities to rise.

Learn More

Fossil fuels: brainly.com/question/13660400

Keyword: Farming, industry, fossil fuel

#LearnwithBrainly

3 0
2 years ago
How much refrigerant must a system contain
Scrat [10]
About 10% to 15% of system charge
7 0
3 years ago
What happens when the difference in charge between a cloud and the ground is too great?
steposvetlana [31]
Lightning strikes the ground

6 0
3 years ago
Read 2 more answers
Although these quantities vary from one type of cell to another, a cell can be 1.9 μm in diameter with a cell wall 60 nm thick.
DaniilM [7]

Answer: 2(10)^{-9} mg

Explanation:

We know the total diameter of the cell (assumed spherical) is:

d=1.9\mu m=1.9(10)^{-6} m

Then its total radius r=\frac{d}{2}=\frac{1.9(10)^{-6} m}{2}=9.5(10)^{-7} m

On the other hand, we know the thickness of the cell wall is r_{t}=60 nm= 60(10)^{-9} m and its density is the same as water (\rho=997 kg/m^{3}).

Since density is the relation between the mass m and the volume V:

\rho=\frac{m}{V}

The mass is: m=\rho V (1)

Now if we are talking about this cell as a thin spherical shell, its volume will be:

V=\frac{4}{3}\pi R^{3} (2)

Where  R=r-r_{w}=9.5(10)^{-7} m - 60(10)^{-9} m

Then:

V=\frac{4}{3}\pi (9.5(10)^{-7} m - 60(10)^{-9} m)^{3} (3)

V=2.952(10)^{-18} m^{3} (4)

Substituting (4) in (1):

m=(997 kg/m^{3})(2.952(10)^{-18} m^{3}) (5)

m=2.94(10)^{-15} kg (6)

Knowing 1 kg=1000 g and 1 mg=0.001 g:

m=2.94(10)^{-15} kg=2(10)^{-9} mg

7 0
3 years ago
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