Register to reply

Angular acceleration

by klm
Tags: acceleration, angular
Share this thread:
klm
#1
Dec4-07, 07:29 AM
P: 167
A 5.0 kg, 60-cm-diameter disk rotates on an axle passing through one edge. The axle is parallel to the floor. The cylinder is held with the center of mass at the same height as the axle, then released.

What is the cylinder's initial angular acceleration?



ok so this is what i think i should do:

Torque= I [tex]\alpha[/tex]

and i need to find the F(weight)= mg = (5)(9.8) = 49 N
radius = .5(.6)= .3
Torque= Fd = 49(.3) = 14.7
14.7 = I [tex]\alpha[/tex]
this is the part which i am not sure on, does I = .5 m r^2 = .5(5)(.3^2) = .225
14.7 .225 [tex]\alpha[/tex]
[tex]\alpha[/tex] = 65.33
but this answer is incorrect, and i do not know where i am making the mistake.
Phys.Org News Partner Science news on Phys.org
Scientists develop 'electronic nose' for rapid detection of C. diff infection
Why plants in the office make us more productive
Tesla Motors dealing as states play factory poker
klm
#2
Dec4-07, 08:04 AM
P: 167
please can someone help
hage567
#3
Dec4-07, 08:03 PM
HW Helper
P: 1,539
Try using the Parallel Axis theorem to find the moment of inertia. This is needed because the axis of rotation is not through the centre of mass of the disk.

[tex]I = I_{CM} + MD^2[/tex]

where [tex]I_{CM}[/tex] is the moment of inertia for a solid disk, M is the mass of the disk and D is the distance from the centre of mass to the new axis.


Register to reply

Related Discussions
Angular Acceleration vs Tangential Acceleration Classical Physics 4
Angular Acceleration Introductory Physics Homework 2
Angular Velocity & Angular Acceleration Introductory Physics Homework 2
Rotational motion -angular energy+angular acceleration Introductory Physics Homework 4
Angular acceleration and linear acceleration Classical Physics 3