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denis-greek [22]
3 years ago
9

Serena is a research student who has conducted an experiment on the discoloration of marble. Read about Serena’s experiment. The

n identify two flaws in her experiment’s design.
Serena sees an article about the Taj Mahal, a medieval marble monument in India. She reads that the white monument is beginning to turn a dull yellow-brown. Serena admires the Taj Mahal and is eager to learn what might be causing the yellowing. She formulates a hypothesis that the yellow-brown tinge may be caused by air pollution from black carbon, brown carbon, or methane, combined with wind erosion.

To test her hypothesis, she decides to study the effects of these air pollutants and wind on white marble. She finds three identical pieces of white marble and exposes one of them to air containing black carbon, one to air with brown carbon, and one to air with methane. She also places a fan on two of the samples, varying the speed of the air stream in regular intervals. After a few days, the marble samples begin changing color, becoming grayish. Serena learns that air pollution caused the discoloration. However, she is not sure how it became gray instead of yellow and what exactly caused the discoloration.

She used identical pieces of marble for her samples.
She introduced at least one confounding variable.
She tried to test multiple hypotheses at a time.
She attributed the marble discoloration to wind erosion.
She used a mechanically-generated air stream rather than natural 
Physics
1 answer:
sergij07 [2.7K]3 years ago
3 0

The two flaws in her experiment’s design are

<span>- She introduced at least one confounding variable.</span> <span>- She tried to test multiple hypotheses at a time</span>

 In the above mentioned experiment she had to have four samples to prove four hypotheses, each one separately and not to mix two hypotheses in an alone sample, that what it brings as consequence is the confusion.

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A 4.79 g bullet moving at 642.3 m/s penetrates a tree trunk to a depth of 4.35 cm. Use work and energy considerations to find th
vladimir1956 [14]

Answer:

Force, F=2.27\times 10^4\ N

Explanation:

Given that,

Mass of the bullet, m = 4.79 g = 0.00479 kg

Initial speed of the bullet, u = 642.3 m/s

Distance, d = 4.35 cm = 0.0435 m

To find,

The magnitude of force required to stop the bullet.

Solution,

The work energy theorem states that the work done is equal to the change in its kinetic energy. Its expression is given by :

F.d=\dfrac{1}{2}m(v^2-u^2)

Finally, it stops, v = 0

F.d=-\dfrac{1}{2}m(u^2)

F=\dfrac{-mu^2}{2d}

F=\dfrac{-0.00479\times (642.3)^2}{2\times 0.0435}

F = -22713.92 N

F=2.27\times 10^4\ N

So, the magnitude of the force that stops the bullet is 2.27\times 10^4\ N

7 0
2 years ago
The highest free-standing tower in North America is the CN Tower in Toronto, Canada. From a distance of 1km from its base, the a
Whitepunk [10]
The height of the tower and the distance from its base form a right angle triangle. Thus,
tan(∅) = height / base
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4 0
3 years ago
I WILL MARK YOU BRAINLIEST FOR A QUICK AND GOOD ANSWER PLEASE NO SPAM what are elastic and inelastic distortion?
Montano1993 [528]
As far as I know, elastic distortion (or elastic deformation or temporary distortion) is the case when an object is deformed by virtue of a cause and after the cause is removed, it regains its original shape in a finite amount of time. If it fails to attain its original shape in finite amount of time or takes infinite time it becomes plastic or permanent distortion.

Inelastic materials, simply put, are non elastic materials. They do not show a fixed trend of deformation vs applied force; in fact, they might not deform at all (rigid materials) or the deformation observed is not completely recoverable; on removal of the applied force, the material doesn't return to its original shape, but to a permanent deformed shape. Such materials are called Plastic materials. 

A typical material like steel shows all these forms under different conditions of loading (applied force). For extremely low magnitudes of forces, it is practically rigid. Increasing magnitudes of force show a linear elastic response, while further increase show a non-linear, plastic response, till rupture occurs when the material breaks.
4 0
2 years ago
Read 2 more answers
Brainliest if right.
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Answer:

the third law (for every action there is an equal and opposite reaction).

Explanation:

The skateboarder pushes backwards on the road (that is he applies a force on the road in a direction opposite the direction of intended motion). By Newton's third law, this action of the skateboarder causes an equal reaction of the road on the skateboarder in the opposite direction. Newton's third law states that action and reaction are equal but opposite in direction. So, the road in response to this backward force pushes the skateboarder in the forward direction causing the skateboarder and the skateboard to move in the forward direction.

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2 years ago
Describe the orientation of magnetic field lines by drawing a bar magnet, labeling the poles, and drawing several lines indicati
CaHeK987 [17]

Answer:

A field is a way of mapping forces surrounding any object that can act on another object at a distance without apparent physical connection. The field represents the object generating it. Gravitational fields map gravitational forces, electric fields map electrical forces, and magnetic fields map magnetic forces.

Explanation:

6 0
2 years ago
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