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10 months ago

11. Why do dark surfaces absorb radiation better than light surfaces?

1 answer:

7 0

When an electromagnetic wave hits a surface the photons transmit part of the energy to the molecules of the surface. When parts of the electromagnetic waves are reflected depending on the wavelength that is reflected our eyes perceive the object as having a lighter or darker color. The more wavelengths are reflected the lighter the color of the object will be. The more wavelengths are absorbed the darker the object will appear to be. Therefore, those materials that absorb more wavelengths will be dark and those that absorb fewer wavelengths will appear lighter.

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The lower the value of the coefficient of friction,the_the resistance to sliding

malfutka [58]

Answer:

lower

Explanation:

The lower the value of the coefficient of friction, the lower the resistance to sliding.

The coefficient of friction is the ratio of the frictional force and the normal force pressing two surfaces in contact together.

U = $\frac{F}{N}$

U is the coefficient of friction

F is the frictional force

N is the normal force

We see that coefficient of friction is directly proportional to frictional force.

7 0

3 years ago

It took a crew 9 h 36 min to row 8 km upstream and back again. If the rate of flow of the stream was 2 km/h, what was the rowing

babunello [35]

Answer:

3 km/h

Explanation:

Let's call the rowing speed in still water x, in km/h.

Rowing speed in upstream is: x - 2 km/h

Rowing speed in downstream is: x + 2 km/h

It took a crew 9 h 36 min ( = 9 3/5 = 48/5) to row 8 km upstream and back again. Therefore:

8/(x - 2) + 8/(x + 2) = 48/5 (notice that: time = distance/speed)

Multiplying by x² - 2², which is equivalent to (x-2)*(x+2)

8*(x+2) + 8*(x-2) = (48/5)*(x² - 4)

Dividing by 8

(x+2) + (x-2) = (6/5)*(x² - 4)

2*x = (6/5)*x² - 24/5

0 = (6/5)*x² - 2*x - 24/5

Using quadratic formula

$x = \frac{2 \pm \sqrt{(-2)^2 - 4(6/5)(-24/5)}}{2(6/5)}$

$x = \frac{2 \pm 5.2}{2.4}$

$x_1 = \frac{2 + 5.2}{2.4}$

$x_1 = 3$

$x_2 = \frac{2 - 5.2}{2.4}$

$x_2 = -1\; 1/3$

A negative result has no sense, therefore the rowing speed in still water was 3 km/h

7 0

3 years ago

According to the "Law of Increasing Opportunity Costs," what would be the opportunity cost of a student who is staying up all ni

kodGreya [7K]

C. The opportunity cost of a student who is staying up all night to study for an exam that he has to take in the early morning is sleep or rest.

<h3>What is law of opportunity cost?</h3>

The law of increasing opportunity cost is an economic principle that describes how opportunity costs increase as resources are applied.

As the student gives up his sleep or night rest in the place of his exam preparation, we say that the opportunity cost is the sleep or rest.

Thus, the opportunity cost of a student who is staying up all night to study for an exam that he has to take in the early morning is sleep or rest.

Learn more about opportunity cost here: brainly.com/question/8846809

#SPJ1

7 0

1 year ago

Which of the following best defines mass?

Radda [10]

"<span>The amount of matter in a substance" is the one among the following choices given in the question that best defines mass. The correct option among all the options that are given in the question is the first option or option "A". I hope that this is the answer that has actually come to your desired help.</span>

5 0

3 years ago

Read 2 more answers

Jerry is conducting an experiment to test friction. His setup is shown below. If he wants to test the friction between different

professor190 [17]

Answer:

The correct option is D

Explanation:

This question is incomplete because of the absence of the setup which as been attached below. The setup shows/determines/tests the friction of wood (which is a block material), since Jerry wants to test the friction between different types of materials, he will have to replace the wooden block with another type of block material of choice so as to determine the friction of that also.

In order to have a comprehensive experiment, Jerry can use 4-5 different types of block material in the course of the experiment.

3 0

3 years ago