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3 years ago

What is the minimum mass needed for a star to be on the main sequence? What happens to stars that do not meet the minimum mass?

1 answer:

6 0

Main sequence stars are characterised by the source of their energy.They are all undergoing fusion of hydrogen into helium within their cores. The mass of the star is the main element for such process or phenomenon to take place for it is a determinant of both the rate at which they perform the said activity and the amount of fuel available.

To answer the question, the lower mass limit for a main sequence star is about 0.08. If the mass of a main sequence star is lower than the above-mentioned value, there would be a deficit or insufficiency of gravitational force to generate a standard temperature for hydrogen core fusion to take place and the underdeveloped star would form into a brown dwarf instead.

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For a particular casting setup, the top of the sprue has a diameter of 0.030 m, and its length is 0.200 m. The volume flow rate

faust18 [17]

Answer with Explanation:

We are given that

Diameter=0.030 m

Length of sprue= $h_1$ =0.200 m

Metal volume flow rate,Q=0.03 $m^3/min$

Q= $\frac{0.03}{60}=5\times 10^{-4}m^3/s$ because 1 minute=60 seconds

Let 1 for the top and 2 for the bottom

$d_=0.030 m$

$h_2=0$

$A_1=\frac{\pi d^2}{4}=\frac{3.14\times (0.030)^2}{4}$

$A_1=7.065\times 10^{-4} m^2$

$v_1=\frac{Q}{A_1}=\frac{5\times 10^{-4}}{7.065\times 10^{-4}}$

$v_1=0.708 m/s$

Pressure at the top and bottom of the sprue is atmospheric

$h_1+\frac{v^2_1}{2g}=h_2+\frac{v^2_2}{2g}$

Substitute the values

$0.2+\frac{(0.708)^2}{2\cdot 9.8}=0+\frac[v^2_2}{2\cdot 9.8}$

$v^2_2=2\cdot 9.8\cdot \frac{0.2\cdot 9.8\cdot 2+0.501264}{2\cdot 9.8}=4.421264$

$v_2=\sqrt{4.421264}=2.1 m/s$

$Q=A_2v_2$

$5\times 10^{-4}=A_2\times 2.1$

$A_2=\frac{5\times 10^{-4}}{2.1}=2.381\times 10^{-4} m^2$

Reynolds number= $\frac{v_2D\rho}{\eta}$

$\eta=0.004 N.s/m^2$

$\rho=2700 kg/m^3$

Substitute the values then we get

Reynolds number= $\frac{2.1\times 0.03\times 2700}{0.004}$

Reynolds number=42525

The Reynolds number is greater than 4000 .Therefore, the flow is turbulent.

8 0

3 years ago

Does the cereal or the milk go first? <br><br>

vazorg [7]

Answer:

Cereal

Explanation:

Nobody puts the milk first that's just communism

7 0

3 years ago

Read 2 more answers

A dentist’s drill starts from rest. After 3.20 s of constant angu-lar acceleration, it turns at a rate of 2.51 3 104 re v/m i n.

Gekata [30.6K]

Answer:

$ΔTita = 4205.6 rad$

Explanation:

$w_{i}$ means initial angular velocity, which is 0 rev/min

$w_{f}$ means final angular velocity, which is $2.513*10^{4}rev/min$

t means time t= 3.20 s

one revolution is equivalent to 2πrad so the final angular velocity is:

$w_{f}$ = (2π/60) *2.513*10^{4} rad/s

$w_{f}$ = 2628.5 rad/s

so the angular acceleration, α will be:

α = 2628.5 rad/s / 3.20 s

$a = 821.40 rad/s^{2}$

so the rotational motion about a fixed axis is:

$w^{2} _{f} =w^{2} _{i}$ + 2αΔTita where ΔTita is the angle in radians

so now find the ΔTita the subject of the formula

ΔTita = $\frac{w^{2} _{f}-w^{2} _{i} }{2a}$

$ΔTita = ((2628.5)^{2} - (0 rev/min)^{2}) / 2* 821.40$

$ΔTita = 4205.6 rad$

7 0

3 years ago

Read 2 more answers

This diagram shows a stationary box sitting on the floor. Which statements about the other force exerted on the box are

Alex777 [14]

It's a normal force exerted by the floor. It balances the gravitational force. Option A is correct. The normal force is balanced by the gravitational force.

<h3>What is the friction force?</h3>

It is a type of opposition force acting on the surface of the body that tries to oppose the motion of the body. its unit is Newton (N). Mathematically it is defined as the product of the coefficient of friction and normal reaction.

On resolving the given force and accelertaion in the different components and balancing the equation gets components in the y-direction.

The normal force is balanced by the gravitational force. It's a normal force exerted by the floor. It balances the gravitational force.

Hence, option A is correct.

To learn more about the friction force refer to the link;

brainly.com/question/1714663

#SPJ1

5 0

2 years ago

How does opening a parachute slow the fall rate of a skydiver?

nexus9112 [7]

Answer:

the air is being stopped in the pocket of the parachutes theys why the parachute has a certain shape so that the air that gets caught inside of it as the skydiver goes down slows down the landing

5 0

3 years ago