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katrin [286]
4 years ago
11

A star is in hydrostatic equilibrium when the outward push of pressure due to core burning is exactly in balance with the inward

pull of gravity. When the hydrogen in a star's core has been used up, burning ceases, and gravity and pressure are no longer in balance. This causes the star to undergo significant changes.
Which of the following evolutionary changes would bring a star back into hydrostatic equilibrium? Check all that apply:

a) A small increase in the star's internal pressure and temperature causes the star's outer layers to expand and cool.
b) A small decrease in the star's internal pressure and temperature causes the star's outer layers to contract and heat up.
c) A small increase in the star's internal pressure and temperature causes the star's outer layers to contract and heat up.
d) A small decrease in the star's internal pressure and temperature causes the star's outer layers to expand and cool.
Physics
1 answer:
viktelen [127]4 years ago
7 0

Answer:

a and b

Explanation:

Hydro static equilibrium holds a star steady and balanced. Whenever a star stops burning hydrogen in its center, there must be evolutionary improvements to maintain equilibrium for the star Of example, if a star's internal pressure and temperature fall, gravity will take over and force the star to contract and heat up, restoring stability. By contrast, if a star's internal pressure and temperature rises, the extra pressure causes the star to widen and cool, restoring balance.

so, according to above explanation options a and b both are true

a) A small increase in the star's internal pressure and temperature causes the star's outer layers to expand and cool.

b) A small decrease in the star's internal pressure and temperature causes the star's outer layers to contract and heat up.

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Answer:

the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.

Explanation:

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3 years ago
The current through a certain heater wire is found to be fairly independent of its temperature. If the current through the heate
bearhunter [10]

Answer:

(c) increase by a factor of four

Explanation:

the formular for the relationship between  energy and current is E= I²Rt (Heat energy)

the heater is fairly independent of its temperature , and given the time to be constant.

with the current being doubled,

E = I² Rt

E/ I² = K

\frac{E1}{I1^{2} } =\frac{E2}{I2^{2} }

E2 = \frac{E1* I1^{2} }{I1^{2} }

I2 = 2* I1

E2 =  E1 * 4*I1² / I1²

dividing , we have that  E2 = 4 * E1

which means during the same time interval the amount of energy will increase by a factor of four.

7 0
4 years ago
Pelicans tuck their wings and free-fall straight down whei} diving for fish. Suppose a pelican starts its dive from q height of
Dominik [7]

Answer:

3.3 m

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration due to gravity = 9.81 m/s²

v^2-u^2=2as\\\Rightarrow v=\sqrt{2as+u^2}\\\Rightarrow v=\sqrt{2\times 9.81\times 16+0^2}\\\Rightarrow v=17.72\ m/s

v=u+at\\\Rightarrow 17.72=0+9.81\times t\\\Rightarrow \frac{17.72}{9.81}=t\\\Rightarrow t=1.81 \s

The fish needs to see the pelican before 0.2 seconds in order to escape so the time pelican has is 1.81-0.2=1.61 seconds

In that time the pelican would have traveled

s=ut+\frac{1}{2}at^2\\\Rightarrow s=0\times 1.61+\frac{1}{2}\times 9.81\times 1.61^2\\\Rightarrow s=12.71\ m

So, the pelican would be 16-12.71 = 3.3 m above the water.

6 0
3 years ago
How does the mass of an object change the gravitational pull on two objects in a system? How does the distance between objects i
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Answer:The greater the mass, there greater then gravitational pull on their objects.

There greater the distance,the lower the gravitational pull between the object

Explanation:

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4 0
3 years ago
1. A bicycle initially moving with a velocity
ki77a [65]

Answer:

\boxed {\boxed {\sf 15 \ m/s \ or \ 15 \ m*s^{-1}}}

Explanation:

We are asked to find the final velocity. We are given the acceleration, time, and initial velocity, so we can use the following kinematics formula.

v_f= v_i+ at

In this formula, v_f is the final velocity, v_i is the initial velocity, a is the acceleration, and t is the time.

The bicycle has an initial velocity of 5.0 m *s⁻¹ or m/s, acceleration of 2 m/s², and a time of 5 seconds.

\bullet \  v_i = 5.0 \ m/s \\\bullet \  a= 2\ m/s^2\\\bullet \  t= 5  \ s

Substitute the values into the formula.

v_f=5.0 \ m/s + ( 2\ m/s^2 * 5 \ s)

Solve inside the parentheses.

  • \frac {2 \ m}{s^2}* 5 \ s = \frac{ 2 \ m}{s} * 5 = \frac{ 10 \ m}{s} = 10 \ m/s

v_f= 5.0 \ m/s + (10 \ m/s)

Add.

v_f= 15 \ m/s

The units can also be written as:

v_f= 15 \ m*s^{-1}

The bicycle's final velocity is 15 meters per second.

7 0
3 years ago
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