1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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