Class Management i Help Practice Assignment 8 (CH 8) Begin Date: 10/29/2017 6:00
ID: 1787866 • Letter: C
Question
Class Management i Help Practice Assignment 8 (CH 8) Begin Date: 10/29/2017 6:00:00 AM -- Due Date: 11/25/2017 11:59:00 PM End Date: 11/26/2017 1:00:00 AM (8%) Problem 6: You have a horizontal grindstone (a disk) that is 89 kg, has a 0.34 m radius, is turning at 88 rpm (in the positive direction), and you press a steel axe against the edge with a force of 21 N in the radial direction ©theexpertta.com 50% Part (a) Assuming that the kinetic coefficient of friction between steel and stone is 0.20, calculate the angular acceleration of the grindstone in rad/s2 Grade Summary Deductions 100% = 10.2611 7 8 9 HOME Submissions Attempts remaining: 3 (0% per attempt) detailed view cotan0 asin0 acosO atan0 aon sinh0 coshO tnhcotanh0 + 0% 0% 0% 0% 0 END °Degrees Radians O BACKSPACE DELCLEAR 4 Submit Hint I give up Hints: 0% deduction per hint. Hints remaining:- Feedback:-deduction per feedback - 50% Part (b) What is the number of turns, N, that the stone will make before coming to rest?Explanation / Answer
(A) F = 21 N
f = uk F
and torque = I alpha
- uk F R = ( M R^2 / 2) alpha
alpha = - 2 uk F / M R
= - (2 x 0.20 x 21) / (89 x 0.34)
= - 0.28 rad/s^2
(b) w0 = 88 rpm = 88 x 2pi rad/ 60 s = 9.22 rad/s
wf^2 - wi^2 = 2 alpha theta
0^2 - 9.22^2 = 2(-0.28) (theta)
theta = 151.6 rad
turns = theta / 2pi = 24 turns