Need Help Solving Physics Problems - Any Assistance Appreciated!

[axedodger]

Having significant issues with solving these problems. Any help is appreciated. Thanks to all who can help!

1. How large must the coefficient of static friction be between the tires and the road if a car is to round a level curve of radius 75 m at a speed of 90 km/h?


I used the equation: μs = v^2/gr

answer: 0.85 was told it was wrong? alternatives?




2. Calculate the force of Earth's gravity (in N) on a spacecraft 12,800 km (2 Earth radii) above the Earth's surface if its mass is 1600 kg.

Note: Your answer is assumed to be reduced to the highest power possible.

I am terrible with powers of 10. Any help is appreciated.


I used eq. F = G m(satellite)m(earth)/2r^2

I also tried F = G m(satellite)m(earth)/3r^2

answer: one of my answers 0.00017x10^8



3. A certain neutron star has five times the mass of our sun packed into a sphere about 10 km in radius. Estimate the surface gravity on this monster (in m/s2).

Note: Your answer is assumed to be reduced to the highest power possible.


Don't even knwo where to begin with this problem.




4. A space shuttle releases a satellite into a circular orbit 650 km above the Earth. How fast must the shuttle be moving (relative to Earth) when the release occurs (in m/s)?



equation used: V = √Gm(earth)/r

answer: v = 0.005673769x10^11 m/s

also go an answer of v = 23819 m/s




5. During an Apollo lunar landing mission, the command module continued to orbit the Moon at an altitude of about 100 km. How long did it take to go around Moon once (in seconds)?


Don't know where to begin here either.







THANKS TO ALL WHO CAN HELP!

PLease let me know what question your helping with if you answer. THANKS!

 

[HallsofIvy]

Having significant issues with solving these problems. Any help is appreciated. Thanks to all who can help!

1. How large must the coefficient of static friction be between the tires and the road if a car is to round a level curve of radius 75 m at a speed of 90 km/h?I used the equation: μs = v^2/gr

answer: 0.85 was told it was wrong? alternatives?

What is "s" here? Why did you use that equation? What was your reasoning?

2. Calculate the force of Earth's gravity (in N) on a spacecraft 12,800 km (2 Earth radii) above the Earth's surface if its mass is 1600 kg.

Note: Your answer is assumed to be reduced to the highest power possible.

I am terrible with powers of 10. Any help is appreciated.

I don't see that "powers of 10" have anything to do with this.
$$F= \frac{GmM}{r^2}$$
You know that the acceleration due to gravity at the surface of the Earth is -9.88 m/s^2 so $GM/R^2= 9.88$ where R is the radius of the earth. replace R with 2R.

3. A certain neutron star has five times the mass of our sun packed into a sphere about 10 km in radius. Estimate the surface gravity on this monster (in m/s2).

Again, you know that $GM/R^2= 9.88$. Replace M by 5 M and replace R by (10/640000)R.

Note: Your answer is assumed to be reduced to the highest power possible.

4. A space shuttle releases a satellite into a circular orbit 650 km above the Earth. How fast must the shuttle be moving (relative to Earth) when the release occurs (in m/s)?

The distance from the center of the Earth is 6400+ 650 km. What is the circumference of a circle of that radius? What is the speed of a satellite that goes that far in 24 hours?

5. During an Apollo lunar landing mission, the command module continued to orbit the Moon at an altitude of about 100 km. How long did it take to go around Moon once (in seconds)?

Much the same as (4). What is the circumference of a circle of radius the radius of the moon plus 100?

THANKS TO ALL WHO CAN HELP!

PLease let me know what question your helping with if you answer. THANKS!

You really need to show some of YOUR work in the future.

 

[axedodger]

sorry question 1 ... μs = coefficient of static friction

I used μs = v^2/gr because that is the equation derived from μ(static)mg = mv^2/r

 

[axedodger]

I edited the work to show what I knew(which was limited).