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VladimirAG [237]
3 years ago
8

Which is true regarding AC current? The electrons move back and forth. The +/- polarity is constant. It is common in portable de

vices. It can only produce low voltages.
Physics
2 answers:
Rus_ich [418]3 years ago
8 0
A. The electrons move back and forth.
Hope this helped. :L
andre [41]3 years ago
7 0

Answer: Option (a) is the correct answer.

Explanation:

AC current stands for alternating current. In an alternating current there is periodically reverse movement of current.

This means electrons move in one direction for a certain time and then they reverse their movement for the same time period and it continues in the back and forth position.

Thus, we can conclude that the statement electrons move back and forth is true regarding AC current.


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What scientisists stated that animals, as well as plants, are made of cells.?
Andrews [41]
<span>The answer is Mathias Schleiden and <span><span>Theodor Schwann</span></span></span>
7 0
3 years ago
7. Two people are pushing a 40.0kg table across the floor. Person 1 pushes with a force of 490N
artcher [175]

Answer:

20.4 m/s^{2}

Explanation:

To start doing this problem, first draw a free body diagram of the table. My teacher always tells us to do this, and I find that it is very helpful. I have attached a free body diagram to this answer- take a look at it.

First, let us see if Net force = MA. To do that, we need to determine whether the object is at equilibrium horizontally. For an object to be at equilibrium, it either needs to be moving at a constant velocity or not moving at all. Also, if an object is at equilibrium, there will not be any acceleration. But we know that there IS acceleration horizontally, so it cannot be in equilibrium. If it is not in equilibrium, we can use the formula ∑F= ma.

Let us determine the net force. Since the object is moving horizontally, we can ignore the weight and normal force, because they are vertical forces. The only horizontal forces we need to worry about are the applied force and force of friction.

Applied force = 1055 N (490 + 565)

Friction force= Unknown

To find the friction force, use the kinetic friction formula, Friction = μkN

μk is the coefficient, which the problem includes- it is 0.613.

N is the normal force, which we have to find.

*To find the normal force, we have to determine if the object is at equilibrium VERTICALLY. Since it has no acceleration vertically (it's not moving up/down), it is at equilibrium. Now, when an object is at equilibrium in one direction, it means that all the forces in that direction are equal. What are our vertical forces? Weight (mg) and Normal force (N). So it means that the Normal force is equal to the Weight.

Weight = mg = (40)(9.8) = 392 N

Normal force = 392 N

Now, plug it back into the formula (μkN): (0.613)(392) = 240.296 N

Friction = 240.296 N

Now that we know the friction, we can find the horizontal net force. Just subtract the friction force, 240.296 from the applied force, 1055 N

Horizontal Net Force: 814.704 N

Now that we know the net force, plug in the numbers for the formula

∑F= ma.

814.704 = (40.0)(a)

*Divide on both sides)

a = 20.3676 m/s^2

Round it to 3 significant figures, to get:

20.4 m/s^{2}

7 0
3 years ago
A 20 metric ton train moves toward the south at 50 m/s. At what speed must it travel to have four times its original momentum
OverLord2011 [107]

Answer:

200 m/s

Explanation:

as momentum is a product of mass and speed, and mass is not changing, four times the speed will result in four times the momentum.

p = mv

4p = m(4v)

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According to scientists, the first fossil of a jellyfish first appeared approximately 500 million years ago. Or to be more exact, the Cambrian Period.

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