# Find the Formulas to Solve Homework Questions

• 2odd
In summary, the conversation discusses various questions related to physics and astronomy. The questions include finding the mass of the galaxy, determining the distance of a new galaxy, calculating spacetime interval, finding the Schwartzschild radius of a black hole, and determining the time required for a black hole to evaporate by Hawking Radiation. The conversation emphasizes the importance of having the necessary formulas and equations to solve these questions.
2odd
Can anyone give me the formula or equation so I can solve each of these?

## Homework Statement

Question #1
Suppose the Sun is located 7.4 kiloparsecs from the center of the Milky Way galaxy, and that it orbits the galaxy at a velocity of 240 km/sec. Estimate the mass of the galaxy interior to the Sun's orbit, converted to solar masses.

____solarmasses

Question #2
A new distant galaxy is discovered which shows a redshift corresponding to a recession velocity of 4429.0 kilometers/second. Using Hubble's Law, and a value of H = 72 km/s per Mpc, what is the distance to the new galaxy in megaparsecs?

____Mpc

Question #3
Find the invariant spacetime interval for a particle that travels sideways (in the x-direction only) a distance of 1000 kilometers in 0.1 seconds.

____meters

Question #4
What is the Schwartzschild radius of a typical stellar remnant black hole with a mass of 18.57 solar masses?

____meters

Question #5
What is the time required for a black hole with a mass of 5.13 x 1029 kilograms to evaporate by Hawking Radiation?

____years

Question #6
What is the temperature of a typical stellar remnant black hole with a mass of 16.32 solar masses?

____Kelvins

## Homework Equations

I don't know the formula to solve them.

## The Attempt at a Solution

I can't do any attempts yet because I don't have the formulas.

Well, you could start by making an attempt to locate the formulas you need in your textbook or class notes.

For the first one, you could use the approximation which says that for the orbit to be stable and circular, the centripetal force needs to be equal to the gravitational force. Find the formulas for those and equate them.

For the next questions, all you need to do is look up Hubble's law, the formula for spacetime interval, Schwarzschild radius, and so on.

Certainly your professor doesn't expect you to figure this out all by yourself... don't you have a textbook?

## 1. What is the process for finding formulas to solve homework questions?

The process for finding formulas to solve homework questions varies depending on the subject and type of question. Generally, it involves analyzing the given information, identifying what is being asked, and then using equations and known principles or patterns to solve for the unknown variable.

## 2. How do I know which formula to use for a specific homework question?

To determine which formula to use, read the question carefully and look for keywords or phrases that indicate the type of problem. It can also be helpful to review your class notes or textbook for similar problems and the formulas used to solve them.

## 3. Can I use a formula I found online to solve a homework question?

In most cases, it is best to use the formulas provided by your teacher or textbook. However, if you are unsure or need additional help, you can consult reputable online sources or ask your teacher for guidance.

## 4. What should I do if I am stuck on a homework question and cannot find a formula to solve it?

If you are having trouble finding a formula to solve a homework question, try breaking down the problem into smaller parts and see if you can solve them separately. You can also seek help from a classmate, teacher, or tutor for additional support.

## 5. Is it important to memorize formulas for homework questions?

While it is always helpful to have a strong understanding of formulas, it may not always be necessary to memorize them. Focus on understanding the concepts and principles behind the formulas, and you will be better equipped to solve a variety of homework questions.

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