Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the speed of the disk?

  1. Feb 27, 2007 #1
    I have not attempted to work on these, the only attempt i've done was look and stare at the questions and not know where to start or even begin the problem. I do not know which formula to use either. given is highlighted in bold lettering. Unfortunately i have other homework and these problems are due tommorow so urgent help is needed thx!

    3. .050kg disk attached to the end of a .150-m wire revovles uniformly on a flat, frictionless surface.

    a) moving 3 revolutions per second, what is the force exerted by the wire on the object?

    b)What is the speed of the disk?

    4.How large must the coefficent of friction be between the tires and the road if the car is to round a level curve of radius 85m at a speed if 95 km/h?

    6. A satilite is place in orbit 6.00x10^6. Jupiter has a mass of 1.90x10^7 and radius of 7.5x10^7. Find the orbital speed.

    7. The outer radius of saturns rings are 170,000. Find the period of the outer radius.
  2. jcsd
  3. Feb 27, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    You need to show at least some effort before we can help you! I find it hard to believe that you have no equations in your text book or class notes that will help you on these problems.
  4. Feb 27, 2007 #3
    The hardest problem for me is deciding which formula to use and if i ussualy find the formula i can plug the numbers in the problem and solve it. Here is what i have probaly isn't right lols if it is OMG for me !!!!lols
    3. Still have no clue on the formula for this one.

    4. v^2 = 95^2
    ----- ------ = 106.18
    r 85
    6. GMm
    -------------------------------------- = 1.01384x10^-4
    7. F = m v^2 / r
    I have no clue if this is the right formula and what to plugin lols..
  5. Feb 27, 2007 #4
    6. A satilite is place in orbit 6.00x10^6. Jupiter has a mass of 1.90x10^7 and radius of 7.5x10^7. Find the orbital speed.

    ...6 x 10^6 Whats? Meters? Lemons?
  6. Feb 27, 2007 #5
    Your problems all sound like applications of Newton's Laws of motion. Here is a basic strategy:
    1. Draw a picture, draw the system(object) of interest large and show any interaction(s) with the environment.
    2. Draw the forces acting on your system. Might wanna choose a coordinate system to work in now.
    3. Apply Newton's second in each direction. Stare at the picture to determine what you might be able to say about the acceleration in any direction. :bugeye:
    4. Solve. This depends on the problem. You should remember formulae like that for the circumference of a circle or what the frictional force depends on, etc. Having these memorized will help you think about getting to the solution through a series of steps, hopefully.
    Good luck. :approve:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook