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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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An astronaut stands on the surface of an asteroid. The astronaut then jumps such that the astronaut is no longer in contact with
Anna71 [15]

(D) The gravitational force between the astronaut and the asteroid.

Reason :

All the other forces given in the options, except (D), doesn't account for the motion of the astronaut. They are the forces that act between nucleons or atoms and neither of them accounts for an objects motion.

6 0
3 years ago
PRACTICE ANOTHER A cube of wood having an edge dimension of 19.7 cm and a density of 647 kg/m3 floats on water. (a) What is the
dedylja [7]

CHECK COMPLETE QUESTION

The cube of wood having an edge dimension of 19.7cm and a density of 647kg/m3 floats on water

(a) What is the distance from the horizontal top surface of the cube to the water level answer in cm

(b) What mass of lead should be placed on the cube so that the top of the cube will be just level with the water surface answer in kg

Answer:

a)6.29cm

b)2.78 kg

Explanation:

Given:

Let us calculate the volume first, we were given dimension as 19.7cm=0.197m

Volume is (0.197 meters)³ = 0.00764m³

Then we can calculate the mass as;

Given mass is 647 kg/m³ x 0.00774m³ = 4.947kg

The weight = mass × acceleration due to gravity

weight = 4.947 x 9.8 N/kg = 48.44N

By Floating we can say the the buoyancy force has to equal the weight (48.44 N) which has

which is equal to the weight of volume of the displaced water. Or the mass, the calculation is the same.

We know that density of fresh water at 20ºC is 998 kg/m³

Then we can calculate the volume of displaced water as

4.947 kg / 998 kg/m³ = 0.00496 m³

We know that the displaced water has a shape of a rectangular solid with 0.197 meters on the two horizontal dimensions, and h as the height to the surface then

V = 0.197²h = 0.00496

0.00496= 0.197²h

h = 0.1278 meters or 12.78 cm

Then the the distance exposed, would be 19.7–12.78 = 6.29 cm

b) ifthe cube is fully submerged, the volume of the displaced water is 0.00774m³

mass of displaced water is 0.00774m³ x 998 kg/m³ = 7.724 kg

Added mass is the mass of the displaced water – mass of block

= 7.724–4.947 = 2.78 kg

5 0
3 years ago
How does the current in a circuit change if the resistance is doubled? The current is halved. The current is doubled. The curren
Inessa05 [86]

Answer:

The current is halved

Explanation:

The relationship between the current and the resistance is given by Ohm's Law, as follows:

V = IR\\I = \frac{V}{R}

where,

V = Voltage

I = Current

R = Resistance

Therefore, if we double the resistance:

I' = \frac{V}{2R}\\\\I' = \frac{1}{2}I

Hence the correct option is:

<u>The current is halved</u>

7 0
3 years ago
Read 2 more answers
65. A length of wire is bent into a closed loop and a magnet is plunged into it, inducing a voltage and, consequently, a current
natulia [17]

Answer:

Resistance of the second wire is twice the first wire.

Explanation:

Let us first see the formula of resistance;

R = pxL/A

Here L is the lenght of the wire, A the area and p is the resistivity of wire.

As we are given that the length of second wire is double than that of the first wire, hence the resistance of second wire would be double.

Since we have two loop in second case, inducing double voltage but as resistance is doubled so the current would remain same according to ohms law

I = V/R

6 0
3 years ago
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What determines an object’s thermal energy
Tems11 [23]

Answer:

temperature and mass

Explanation:

  • The higher the temperature of a given quantity of a substance, more is its thermal energy.

  • If a substance contains more mass, this also implies that the object has more particles in it . hence, it has high thermal energy.

<em><u>A</u></em><em><u>d</u></em><em><u>d</u></em><em><u>i</u></em><em><u>t</u></em><em><u>i</u></em><em><u>o</u></em><em><u>n</u></em><em><u>a</u></em><em><u>l</u></em><em><u> </u></em><em><u>I</u></em><em><u>n</u></em><em><u>f</u></em><em><u>o</u></em><em><u>r</u></em><em><u>m</u></em><em><u>a</u></em><em><u>t</u></em><em><u>i</u></em><em><u>o</u></em><em><u>n</u></em><em><u> </u></em>:

  • Temperature is a measure of the average kinetic energy of the particles of a substance.

  • The thermal energy of an object depends on three factors:

  1. number of molecules in the object
  2. temperature of the object.
  3. thermal energy it has.
3 0
3 years ago
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