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elena-14-01-66 [18.8K]
3 years ago
9

A body at rest will remain at rest unless acted on by a(an) _____.

Physics
1 answer:
andrew11 [14]3 years ago
4 0
The answer is A. external, unbalanced force.
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A freight train consists of two 8.00 \times 10^5~\text{kg}8.00×10 ​5 ​​ kg engines and 45 cars with average masses of 5.50 \time
erma4kov [3.2K]

Answer:

F₁ = 4.29 x 10⁵ N

Explanation:

The total force required to move the freight train with the given acceleration is given by the following formula:

F = ma + f

where,

F = Total Force Required from both engines = ?

m = equivalent mass of system = 2(8 x 10⁵ kg) + 5.5 x 10⁵ kg = 21.5 x 10⁵ kg

a = required acceleration = 5 x 10⁻² m/s²

f = force of friction = 7.5 x 10⁵ N

Therefore,

F = (21.5 x 10⁵ kg)(0.05 m/s²) + 7.5 x 10⁵ N

F = 8.575 x 10⁵ N

Now, for identical forces in each engine can be given as:

Force exerted by each engine = F₁ = F/2

F₁ = 8.575 x 10⁵ N/2

<u>F₁ = 4.29 x 10⁵ N</u>

3 0
3 years ago
If planet A is four times as far from the sun as planet C, then the period of its orbit will be__ times as long
Burka [1]
Within the system of the same star, the period of a planet's orbit is
proportional to the 3/2 power of its distance from the central body.
(Kepler's empirical third law of planetary motion, promoted to being
etched in stone by Newton's gravitation.)

(4) ^ 3/2 = <em>8 times</em> as long.
4 0
4 years ago
The point on the earth's surface directly above the point where the fault first ruptures is called the ____________.
Minchanka [31]
This point is called the epicenter. The epicenter is important when it comes to the Earth's surface, because it pinpoints where Earthquakes begin to take shape and occur. It is the place where the most damage is caused by an earthquake and is found above the hypocenter.
8 0
3 years ago
Please i need the answer of this question
frez [133]

Answer:

i think it is f i could be wrong-

6 0
3 years ago
Is a neutron star also a black hole?
coldgirl [10]

No.  A neutron star is the weird remains of a star that blew its outer layers off
in a nova event, and then had enough mass left so that gravity crushed its
electrons into its protons, and then what was left of it shrank down to a sphere
of unimaginably dense neutron soup.  But it didn't have enough mass to go
any farther than that.

A black hole is the remains of a star that had enough mass to go even farther
than that.  No force in the universe was able to stop it from contracting, so it
kept contracting until its mass occupied no volume ... zero.  It became even
more weird, and is composed of a substance that we don't know anything about
and can't describe, and occupies zero volume.

Contrary to popular fairy tales, a black hole doesn't reach out and "suck things in".
It's just so small (zero) that things can get very close to it.  You know that gravity
gets stronger as you get closer to an object, so if the object has no size at all, you
can get really really close to it, and THAT's where the gravity gets really strong.
You may weigh, let's say, 100 pounds on the Earth.  But you're like 4,000 miles
from the center of the Earth.  What if all of the earth's mass was crammed into
the size of a bean.  Then you could get 1 inch from it, and at that distance from
the mass of the Earth, you would weigh 25,344,000,000 pounds. 
But Earth's mass is not enough to make a black hole.  That takes a minimum
of about 3 times the mass of the sun, which is right about 1 million times the
Earth's mass.   THEN you can get a lightweight black hole.
Do you see how it works now ?

I know.  It all seems too fantastic to be true. 
It sure does.

8 0
3 years ago
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