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

Homework Help: Phyicss Hw Help

  1. Oct 13, 2005 #1
    Any help would be appreciated. I have the answers to these problems but can't seem to fully work through them. Well here they are:

    #1) A 5.0 g coin is placed 15 cm from the center of a turntable. The coin has static and kinetic coefficients of friction iwth the turntable surface of static friction=0.80 and kinetic friction=0.50. The turntable very slowly speeds up to 60 rpm. Does the coin slide off?

    The answer is no. But I am not sure how to get there. I converted 60 rpm to radians per second and figured the maximum static friction before the coin will move is 0.0392 (0.80*0.049). I tried to figure what the force on the penny would be by using Newton's 2nd law: sum of the forces in the r direction=mass*angular velocity*radius (0.005*(2*PI)^2)(0.15). Is any of this right?

    #2) Wheat is poured onto a convyor belt at a steady rate of 30 kg/s. What force must be exerted to keep the belt moving at a constant speed of 2.0 m/s? Any help on this one would be appreciated. I am not sure how to even start attacking this one.
  2. jcsd
  3. Oct 13, 2005 #2


    User Avatar
    Homework Helper

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook