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olga nikolaevna [1]
3 years ago
11

What current is used to power the Untied States power grid? O alternating current O direct current​

Physics
2 answers:
QveST [7]3 years ago
4 0

Answer:

alternating

Explanation:

it was right on my quiz

Alina [70]3 years ago
3 0

Answer:

Alternating

Explanation:

It is alternating because it is easy to distribute long distance.

Direct current is found in batteries and have large voltage drop over distance.

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Compare the force of air resistance and the force of gravity on an object falling at its terminal velocity.
Sholpan [36]
The viscous force on an object moving through air is proportional to its velocity.
The only forces acting on an object when falling are air resistance and its weight itself. The weight acts vertically downwards whereas air resistance acts vertically upward.
Let F be the viscous force due to air molecules, B be buoyant force due to air and W be the weight of falling object. Initially, the velocity of falling object and hence the viscous force F is zero and the object is accelerated due to force
(W-B). Because of the acceleration the velocity increases and accordingly the viscous force also increases. At a certain instant, the viscous force becomes equal to W-B. The net force then becomes zero and the object falls with constant velocity. This constant velocity is called terminal velocity.
Thus at terminal velocity, air resistance and force of gravity becomes equal.
7 0
3 years ago
Assume: The bullet penetrates into the block and stops due to its friction with the block. The compound system of the block plus
charle [14.2K]

Answer:

The total energy of the composite system is 7.8 J.

Explanation:

Given that,

Height = 0.15 m

Radius of circular arc = 0.27 m

Suppose, the entire track is friction less. a bullet with a m₁ = 30 g mass is fired horizontally into a block of wood with m₂ = 5.29 kg mass. the acceleration of gravity is 9.8 m/s.

Calculate the total energy of the composite system at any time after the collision.

We need to calculate the total energy of the composite system

Total energy of the system at any time = Potential energy of the system at the stopping point

E=mgh+Mgh

E=(m+M)gh

Put the value in to the formula

E=(30\times10^{-3}+5.29)\times 9.8\times0.15

E=7.8\ J

Hence, The total energy of the composite system is 7.8 J.

8 0
3 years ago
1. why did aristarchus choose the time of a half (quarter) moon to make his measurements for calculating the earth-sun distance?
Stells [14]

In order to make his measurements for determining the Earth-Sun distance, Aristarchus waited for the Moon's phase to be exactly half full while the Sun was still visible in the sky. For this reason, he chose the time of a half (quarter) moon.

<h3 /><h3>How did Aristarchus calculate the distance to the Sun?</h3>

It was now possible for another Greek astronomer, Aristarchus, to attempt to determine the Earth's distance from the Sun after learning the distance to the Moon. Aristarchus discovered that the Moon, the Earth, and the Sun formed a right triangle when they were all equally illuminated. Now that he was aware of the distance between the Earth and the Moon, all he needed to know to calculate the Sun's distance was the current angle between the Moon and the Sun. It was a wonderful argument that was weakened by scant evidence. Aristarchus calculated this angle to be 87 degrees using only his eyes, which was not far off from the actual number of 89.83 degrees. But when there are significant distances involved, even slight inaccuracies might suddenly become significant. His outcome was more than a thousand times off.

To know more about how Aristarchus calculate the distance to the Sun, visit:

brainly.com/question/26241069

#SPJ4

7 0
1 year ago
which statement below is FALSE? A Gravity acts on any object with mass. B The closer objects are, the stronger the gravitational
GenaCL600 [577]

Answer:

Explanation:

5 0
3 years ago
Use newton's laws to find an expression for the net external force acting on the car. ignore air resistance.
alexira [117]
Hi, thank you for posting your question here at Brainly.

Newton's second law of motion can be expressed as Fnet = ma. The next external for acting on, say for example, a moving car are the following:

*weight due to gravity (force down)
*friction force between he road and the car's tires (force opposite the car's direction)

4 0
3 years ago
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