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GalinKa [24]
3 years ago
6

Stars form from clouds of gas and dust. As a protostar gravitationally contracts within its parent cloud, "conservation of angul

ar momentum" says thatA) the protostar rotates more slowly.b) the protostar\'s rotation does not change.c) the protostar\'s axis of rotation will change direction.d) the protostar rotates more quickly.
Physics
1 answer:
vredina [299]3 years ago
5 0

Answer:

D) True. the protostar rotates more quickly.

Explanation:

If the system is isolated, the angular momentum must be retained.

Initial

        L₀ = I w₀

Final

       L_{f} = I_{f}  w_{f}

      L₀ = L_{f}

      I w₀ = I_{f}w_{f}

     w_{f}  = I /I_{f} w₀

In general, the radius of the cloud decreases significantly to form the star, the moment of inertia must decrease, so the angular velocity must increase

Let's examine the answers

A) False. The opposite happens

B) False. Speed ​​changes

C) False. For this there must be an external force, which does not exist

D) True. You agree with the above

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A flat uniform circular disk (radius = 2.30 m, mass = 1.00 ✕ 102 kg) is initially stationary. The disk is free to rotate in the
Vadim26 [7]

The resulting angular speed = 0.6 rad / s.

<u>Explanation:</u>

Here there is no external torque acting on the system thus we can apply the law of conservation of angular  momentum  

Angular momentum of the man = Iω

Where I = Inertia of the man about the axis of rotation

or         I = M r 2

            I  = 50 * 1.25*1.25 = 78.125

w = Angular velocity of the man, that can be calculated as follows

Tangential velocity of man = v = 2m/s  

So time taken to describe this circle is t = (2*pi* r) / v

Now angle described in 1 revolution θ = 2*pi radians

This angle is subtended in time t = (2*pi* r) / v

Thus angular speed = w = θ/t = 2*pi* ( v/ 2π r) = v/r = 2.70 / 1.25 = 2.16 rad/s

So angular momentum of man = Iw = 78.125 * 2.16 = 168.75.

To conserve the angular momentum before and after,

Angular momentum of disk = angular momentum of the man  

           i.e.             Iw of disk = 168.75

                                disk of I = (disk of M*R^2) / 2

                                              = (1.00 * 102 * 2.30 * 2.30) / 2

                                              = 269.79

                 Thus 269.79 of disk of w = 168.75

      Resulting angular speed of disk = 168.75 / 269.79 = 0.6 ras / s

7 0
3 years ago
The following three hot samples have the same temperature. The same amount of heat is removed from each sample. Which one experi
vlabodo [156]

Answer:

Smallest drop: Water

Largest drop: Dirt

Explanation:

The heat needed to change the temperature of a sample is:

Q=cm\Delta T (1)

with Q the heat (added(+) or removed(-)), c specific heat, m the mass and \Delta T the change in temperature of the sample. So, if we solve (1) for

Sample A:

\Delta T=-\frac{Q}{cm} =\frac{Q}{4186*4.0}

\Delta T=-\frac{Q}{16744}

Sample B:

\Delta T=-\frac{Q}{cm} =\frac{Q}{2700*2.0}

\Delta T=-\frac{Q}{5400}

Sample C:

\Delta T=-\frac{Q}{cm} =\frac{Q}{1050*9.0}

\Delta T=-\frac{Q}{9450}

Note that the numbers 16744, 5400, 9450 are in the denominator of the expression -\frac{Q}{cm} that gives the drop on temperature. so, if Q is the same for the three samples the smallest denominator gives the largest drop and vice versa.

So, the smallest drop is Sample A and the largest is Sample C.

(Important: The minus sign of \Delta T implies the temperature is dropping)

8 0
3 years ago
3. Which of the following magnetic scenarios will repel each
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Answer:

option C (1 and 4)

Explanation:

Like poles repel each other, unlike poles attract each other

7 0
4 years ago
Read 2 more answers
A scientist notices that an oil slick floating on water when viewed from above has many different colors reflecting off the surf
Sati [7]

Answer:

a) The minimum thickness of the oil slick at the spot is 313 nm

b) the minimum thickness be now will be 125 nm

Explanation:  

Given the data in the question;

a) The index of refraction of the oil is 1.20. What is the minimum thickness of the oil slick at that spot?

t_{min = λ/2n

given that; wavelength λ = 750 nm and  index of refraction of the oil n = 1.20

we substitute

t_{min = 750 / 2(1.20)

t_{min = 750 / 2.4

t_{min = 312.5 ≈ 313 nm

Therefore, The minimum thickness of the oil slick at the spot is 313 nm

b)

Suppose the oil had an index of refraction of 1.50. What would the minimum thickness be now?

minimum thickness of the oil slick at the spot will be;

t_{min = λ/4n

given that; wavelength λ = 750 nm and  index of refraction of the oil n = 1.50

we substitute

t_{min = 750 / 4(1.50)

t_{min = 750 / 6

t_{min = 125 nm

Therefore, the minimum thickness be now will be 125 nm

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3 years ago
How are electromagnetic waves that are produced by oscillating charges and sound waves that are produced by oscillating tuning f
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They are both created by waves of different forms of energy... sound is the oscillation of other substances, called a medium, while the electromagnetic waves are oscillating through electromagnetic energy. 
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