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3 years ago

15

During the Dust Bowl in the 1930s, there were huge dust storms caused by drought and wind. Farm areas all across the Midwest wer

e affected by erosion. Many farmers lost the crops on which they depended to make a living and support their families.
How can farmers prevent soil erosion on their farms? Choose the two that apply.

A. Leave roots in the soil after harvesting.
B. Plant trees around the fields to block wind.
C. Harvest all the crops on the farm at once.
D. Pull up the entire plant when they harvest crops.

2 answers:

lisov135 [29]3 years ago

7 0

A. Leave roots in the soil after harvesting
B. Plant trees around the fields to block wind

prisoha [69]3 years ago

5 0

A AND B mark me brainlist

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Lightning heats the surrounding air to ___. A. 30000C B. 300C C. 300000C D. 3000C

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A bolt of lightning<span>, which can reach temperatures of roughly 30,000 kelvins (53,540 degrees Fahrenheit). The sun, on the other hand, is eclipsed in this case, its surface temperature is just 6,000 kelvins (10,340 degrees Fahrenheit)
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3 years ago

Read 2 more answers

The circumference of a sphere was measured to be

professor190 [17]

To solve this problem we will apply the concepts related to the calculation of the surface, volume and error through the differentiation of the formulas given for the calculation of these values in a circle. Our values given at the beginning are

$\phi = 76cm$

$Error (dr) = 0.5cm$

The radius then would be

$\phi = 2\pi r \\76cm = 2\pi r\\r = \frac{38}{\pi} cm$

And

$\frac{d\phi}{dr} = 2\pi \\d\phi = 2\pi dr \\0.5 = 2\pi dr$

PART A ) For the Surface Area we have that,

$A = 4\pi r^2 \\A = 4\pi (\frac{38}{\pi})^2\\A = \frac{5776}{\pi}$

Deriving we have that the change in the Area is equivalent to the maximum error, therefore

$\frac{dA}{dr} = 4\pi (2r) \\dA = 4r (2\pi dr)$

Maximum error:

$dA = 4(\frac{38}{\pi})(0.5)$

$dA = \frac{76}{\pi}cm^2$

The relative error is that between the value of the Area and the maximum error, therefore:

$\frac{dA}{A} = \frac{\frac{76}{\pi}}{\frac{5776}{\pi}}$

$\frac{dA}{A} = 0.01315 = 1.31\%$

PART B) For the volume we repeat the same process but now with the formula for the calculation of the volume in a sphere, so

$V = \frac{4}{3} \pi r^3$

$V = \frac{4}{3} \pi (\frac{38}{\pi})^3$

$V = \frac{219488}{3\pi^2}$

Therefore the Maximum Error would be,

$\frac{dV}{dr} = \frac{4}{3} 3\pi r^2$

$dV = 2r^2 (2\pi dr)$

$dV = 4r^2 (\pi dr)$

Replacing the value for the radius

$dV = 4(\frac{38}{\pi})^2(0.5)$

$dV = \frac{2888}{\pi^2} cm^3$

And the relative Error

$\frac{dV}{V} = \frac{ \frac{2888}{\pi^2}}{ \frac{219488}{3\pi^2} }$

$\frac{dV}{V} = 0.03947$

$\frac{dV}{V} = 3.947\%$

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3 years ago

1.Compare how waves are used to send information.

jeyben [28]

Answer:

1:Radio waves are used to carry satellite signals. These waves travel at 300,000 km/s (the speed of light).

2:The standard methods of communication are speaking or writing by a sender and listening or reading the receiver. Most communication is oral, with one party speaking and others listening. ... A mixed message occurs when a person's words communicate one message, while nonverbally, he or she is communicating something else.

3: Today means of communication has increased such a lot that we can receive or send messages from or to far off places. Various means of communication which we use in the modern world are Posts and Telegraphs, Telephone, Radio and Television, Telex, Fax, Pagers, Email, Newspapers and cinema.

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3 years ago

The frequency of a wave is tripled, while the wave speed is held constant. What happens to the wavelength?

grigory [225]

The wavelength decreases

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3 years ago

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A blow-dryer and a vacuum cleaner each operate with a voltage of 120 V. The current rating of the blow-dryer is 10 A, and that o

Katyanochek1 [597]

Answer:

Part a)

P = 1200 Watt

Part b)

P = 480 W

Part c)

$\frac{E_{bd}}{E_{vc}} = 5 : 2$

Explanation:

Part a)

Power consumed by blow dryer is given as

$P = iV$

here supply voltage is given as

$V = 120 volts$

current rating of blow dryer is given as

$i = 10 A$

$P = (120 V)(10 A)$

$P = 1200 W$

Part b)

Power consumed by vacuum cleaner is given as

$P = iV$

here supply voltage is given as

$V = 120 volts$

current rating of vacuum cleaner is given as

$i = 4 A$

$P = (120 V)(4 A)$

$P = 480 W$

Part c)

Energy consumed in a given interval of time is given as

$Energy = power \times time$

now we have to find the ratio of energy consumed in time interval of 11 minutes

so we have

$\frac{E_{bd}}{E_{vc}} = \frac{P_{bd} t}{P_{vc} t}$

now we have

$\frac{E_{bd}}{E_{vc}} = \frac{1200 W\times 11 min}{480 W \times 11 min}$

$\frac{E_{bd}}{E_{vc}} = 5 : 2$

5 0

4 years ago