Homework Help Forum: Physics College

Posted by Jessica on Thursday, October 29, 2009 at 2:23am.

Experiment in this week (week 8) is to study rotational dynamics. Consider a stainless steel annular disk with an outer radius 63 mm and inner radius 7.4 mm. The mass of the disk is 1340 grams. Keep your answers to at least 4 significant digits. (a) What is the moment of inertia of the stainless steel annular disk? .00266 kg m2 (b) The stainless steel annular disk is allowed to rotate on a frictionless table with the rotation axis at its center. The disk has a small cylinder rigidly mounted at the top concentrically. The cylinder's radius is 12.5 mm, and the mass of the cylinder is negligible. A string is wrapped around the cylinder, and a hanging mass of 20.8 g is tied at the other end of the string. When the mass falls under gravity, it causes the stainless steel annular disk to rotate. Ignoring the string's mass, and assuming that the string's motion is frictionless, what is the angular acceleration of the stainless steel annular disk? rad/s2 (c) What is the angular speed of the stainless steel annular disk 4.1 seconds after the hanging mass is released from rest? rad/s (d) At what speed is the hanging mass falling at this time? m/s (e) What is the kinetic energy of the falling mass at this time? J (f) What is the rotational kinetic energy of the stainless steel annular disk at this time? J (g) How much distance has the hanging mass been falling by this time? m I've gotten the first two but others i'm just lost can someone help?

• Physics College - bobpursley, Thursday, October 29, 2009 at 9:05am

  You know a) and b) c) speed=angularacceleration*time d)tangential speed=angularspeed*radius e) 1/2 m v^2 f) 1/2 I w^2 g) distance=1/2 angularspeed*time^2

  
  

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