Practice_EXAM_3_HG

Practice_EXAM_3_HG - PHYS 172 – Fall 2010 Exam 3 ...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: PHYS 172 – Fall 2010 Exam 3 Hand ­written Portion (30 points total) Write down your recitation time: Name (Print): _______________________________________________________ Signature: __________________________________________________________ Day (either Wed, Th, Fri): PUID: _____________________________________________________________ Time: You will lose points if your explanations are incomplete, ___________________________ if we can’t read your handwriting, or if your work is sloppy. Hand ­Written Problem: Object rolling down an inclined plane An object of mass M, radius R and moment of inertia I rolls without slipping (due to a frictional force of magnitude f, down an inclined plane of length L that is fixed to the ground as shown in the figure below. The object starts from rest a height h above ground level. When the object reaches the bottom of the inclined plane, its center of mass has fallen through a vertical distance h. Take the object as the system in the following analysis. h L θ Ground Level A. (6 points) Treat the object as a point particle. In the space below, draw a force diagram on which all forces acting on the object are shown and labeled. Be certain to define a set of coordinate axes, X and Y. B. (6 points) What is the object’s translational kinetic energy when it reaches ground level? [Hint: Use the Energy Principle to answer this question to express your answer in terms of M, g, θ, L, and f .] C. (6 points) What is the object’s total kinetic energy (translational plus rotational) when it reaches ground level? D. (6 points) Use your answer to part C to find that the speed of the object 2 gh when it reaches ground level is V = . I (1 + ) MR 2 E. (6 points) The object’s moment of inertial can be represented as I = b ! M ! R 2 where b is a dimensionless number associated with the objects geometry. For example, b = 1 for a hoop, 2/5 for a sphere, ½ for a disk, etc. Express your answer in part D in terms of this expression for I, thereby showing that the final speed does not depend on either the object’s mass nor its radius. ...
View Full Document

Ask a homework question - tutors are online