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3 years ago

Which statements describe properties of stars check all that apply

Physics

1 answer:

VikaD [51]3 years ago

7 0

Answer:

Stars produce energy through nuclear fusion.

Stars are massive objects composed of gas.

Stars are composed primarily of hydrogen and helium.

Explanation:

Stars are massive objects that have a large gravitational field, which drives the star to contract on itself, which is why fusion occurs: in the center of the star the nuclei of atoms are already so close due to gravity and high temperatures that bind. This is what is called nuclear fusion and is the energy source of a star.

On the other hand yes, the main elements of a star are hydrogen and helium (two hydrogen nuclei fuse to make helium), this makes the star mainly a huge ball of gas so there is no solid surface where you can stand on.

And about water on a star, that is not possible. Temperatures on stars are very very high that water could not exist in a liquid form on them.

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A child drops a ball from a window. The ball strikes the ground in 3.0 seconds. What is the velocity of the ball the instant bef

inessss [21]

Answer:

29.396988 m/s

Explanation:

Really, it depends on where the child is when he drops the ball - e.g., which planet he is on, and his distance from the center of that planet.

I'll assume that the child is on Earth at sea level at the equator, so that his distance from the geocenter is 6378000 meters.

The acceleration, g, is found from

g = GM/r²

G = 6.6743e-11 m³ kg⁻¹ sec⁻²

M = 5.9724e+24 kg

r = 6.378e+6 m

g = 9.799086 m sec⁻²

An approximate answer is found from an equation from constant acceleration kinematics:

v = gt

t = 3.0 sec

v = 29.397259 m/s

Now, the above method is an approximation that makes the technically incorrect assumption that the acceleration of gravity is a constant throughout the entire fall. You get away with it because the drop is very short. In another situation, it might not be. So it would be nice to develop a more accurate method that does not assume constant gravitational acceleration. For that, we begin with the Vis Viva equation:

v = √[GM(2/r − 1/a)]

Here,

a = the semimajor axis of a plunge orbit, which is equal to half of the apoapsis distance of 6378000+h, where

h = the altitude from which the ball is dropped

We can (using some math) develop the following equation:

t − t₀ = √[d/(2GM)] { √(rd−r²) + d arctan √(d/r−1) }

t − t₀ = 3 sec

r = 6378000 meters

d = r + h

Using an iterative method (e.g. Newton's or Danby's), we can determine that the altitude,

h = 44.0954 meters

So,

d = 6378044.09538 meters

a = d/2 = 3189022.04769 meters

Now we can calculate that

v = 29.396988 m/s

This is the more nearly correct answer because it takes into account the variability of the gravitational acceleration during the fall.

5 0

3 years ago

How does Lenz's Law illustrate the concept that "you can't get

Crazy boy [7]

Answer:

When there is a change in magnetic flux linkage through a loop of wire, an electromotive force is induced in the loop, according to the Faraday-Newmann-Lenz Law:

$\epsilon=-\frac{N\Delta \Phi}{\Delta t}$

where

N is the number of turns in the loop

$\Delta \Phi$ is the change in magnetic flux through the loop

$\Delta t$ is the time elapsed

The negative sign in the formula represents Lenz's Law, and tells us about the direction of the electromotive force.

In fact, the negative sign means that the direction of the induced emf is such that to oppose to the change in the magnetic flux that originated the induced emf.

This is a consequence of the law of conservation of energy: no energy can be created out of nowhere. In fact, when the emf is induced in the loop, electrical energy appears in the circuit; however, this electric energy cannot come out of nowhere. Instead, it is just "created" from the transformation of some other form of energy (for instance, the mechanical energy that is used to move the loop in the magnetic field, and changing its magnetic flux).

The negative sign in Lenz's Law tells exactly this: the direction of the induced emf is such that it opposes the initial change in magnetic flux that generated the induced emf, so that overall the total energy is conserved.

5 0

3 years ago

Apples are stored in a container (width = length = 3.5 ft) that is filled to a depth of 2.75 feet. If the unit density of an app

Agata [3.3K]

Answer:

The mass of the apples in the box are 1145.95 lb.

Explanation:

Given that,

Width = 3.5 ft

length = 3.5 ft

Depth = 2.75 feet

Density = 49.3 lb/ft³

We need to calculate the volume

Using formula of volume

$V=l\times h\times b$

Put the value

$V=3.5\times3.5\times2.75$

$V=33.6875\ ft^3$

We need to calculate the mass

Using formula of density

$\rho=\dfraxc{m}{V}$

$m=\rho\timesV$

Put the value into the formula

$m=49.3\times33.6875$

$m=1660.79\ lb$

But porosity is 31 % so apples is 69% mass of total container.

So, Total mass in pounds is

$M=\dfrac{69}{100}\times1660.79$

$M=1145.95\ lb$

Hence, The mass of the apples in the box are 1145.95 lb.

8 0

3 years ago

The light we see coming from the moon is

kirill115 [55]

The answer would be reflected.

4 0

4 years ago

The x-coordinates of two objects moving along the x-axis are given as a function of time (t). x1= (4m/s)t x2= -(161m) + (48m/s)t

Kitty [74]

The two displacement functions are
x₁ = 4t
x₂ = -161 + 48t - 4t²
where
x₁, x₂ are in meters
t is time, s

The distance between the two objects is
x = x₁ - x₂
= 4t + 161 - 48t + 4t²
x = 4t² - 44t + 161

Write this equation in the standard form for a parabola.
x = 4[t² - 11t] + 161
= 4[ (t - 5.5)² - 5.5² ] + 161
x = 4(t-5)² + 40

Ths is a parabola that faces up and has its vertex (lowest point) at (5, 40).
Therefore the closest approach of the two objects is 40 m.
The graph of x versus t confirms the result.

Answer: The distance of the closest approach is 40 m.

5 0

3 years ago