Re: Physics (check)

Posted by COFFEE on Friday, March 30, 2007 at 4:16am.

A sanding disk with rotational inertia 1.1 x 10^-3 kg*m^2 is attached to an electric drill whose motor delivers a torque of 6 Nm about the central axis of the disk. What are the following values about the central axis at the instant the torque has been applied for 185 milliseconds?

(a) the angular momentum of the disk
_______ kg*m^2/s
(b) the angular speed of the disk
_______ rad/s

--------
my submitted answers were wrong.. and this is what i did/come up with.

185 ms = 0.185 seconds
2pi rad / 0.185 s = 33.96 rad/s (wf)

L = Iwf
L = (1.1 x 10^-3)(33.96)
L = 0.037356

.. am i missing something? .. what am i doing wrong? please show me, thanks!

For Further Reading

* Physics - bobpursley, Friday, March 30, 2007 at 7:54am

You are missing the basic laws of motion.

Torque= inerita* angular acceleration
solve for angular acceleration, then.

wf= wi+ angular acceleration*time

angular momentum= I*wf

=====================

ok, so..

6 N*m = 1.1x10^-3 kg*m x Angular Acceleration
Angular Acceleration = 5454.54

wf = (0) + (5454.54)(0.185)
wf = 1008.09 [which answers part b]

thus

Angular Momentum = (1.1x10^-3)(1008.09)
= 1.108899

You are totally ignoring precision of digits in your answers. I would never put more significant digits (precision) in the answer than in the input data. However, in your defense, I see that the input torque is to only one significant digit, and moment of inertia is two sig digits, and time is three. One wonders. However, putting the answers to seven is a feat of imagination. Otherwise, the work looks ok, I didn't punch the calc on it.

i get what you mean..

and oh!! my answers were right :D
thanks!

  1. 👍
  2. 👎
  3. 👁
  1. My password email account please

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics

    A small disk of radius R1 is mounted coaxially with a larger disk of radius R2. The disks are securely fastened to each other and the combination is free to rotate on a fixed axle that is perpendicular to a horizontal frictionless

  2. Please check solution

    A uniform solid disk with a mass of 40.3 kg and a radius of 0.454 m is free to rotate about a frictionless axle. Forces of 90.0 N and 125 N are applied to the disk (a) What is the net torque produced by the two forces? (Assume

  3. Physics

    A solid disk of mass m1 = 9.4 kg and radius R = 0.25 m is rotating with a constant angular velocity of ω = 36 rad/s. A thin rectangular rod with mass m2 = 3.1 kg and length L = 2R = 0.5 m begins at rest above the disk and is

  4. physics (please check work)

    Four identical particles, each with mass m, are arranged in the x,y plane like a cross. They are connected by light sticks to form a rigid body. If m=2.0kg and a=1.0 m the rotational inertia of this array about the y axis is:

  1. Physics

    A uniform disk with mass m = 8.54 kg and radius R = 1.35 m lies in the x-y plane and centered at the origin. Three forces act in the +y-direction on the disk: 1) a force 333 N at the edge of the disk on the +x-axis, 2) a force 333

  2. physcis

    Disk 1 (of inertia m) slides with speed 2.0 m/s across a low-friction surface and collides with disk 2 (of inertia 2m) originally at rest. Disk 1 is observed to turn from its original line of motion by an angle of 15 ∘, while

  3. physics concepts (please check over my work)

    A uniform cyclinder made of lead has the same mass and the same length as a uniform solid cylinder made of wood. The rotatonal inertia of the lead cylinder compared to the wooden one is: I thought at first that the rotational

  4. Physics please check

    Please tell me where i went wrong. During an all-night cram session, a student heats up a one-half liter (0.50 10-3 m3) glass (Pyrex) beaker of cold coffee. Initially, the temperature is 19°C, and the beaker is filled to the

  1. Physics

    A uniform disk with mass m = 9.42 kg and radius R = 1.31 m lies in the x-y plane and centered at the origin. Three forces act in the +y-direction on the disk: 1) a force 315 N at the edge of the disk on the +x-axis, 2) a force 315

  2. ap physics

    Determine the change in rotational kinetic energy when the rotational velocity of the turntable of a stereo system increases from 0 to 33 rpm. Its rotational inertia is 6.8×10−3kg⋅m2 .

  3. phys

    A disk with a rotational inertia of 2.0 kg.m^2 and a radius of 0.40 m rotates on a frictionless fixed axis perpendicular to the disk faces and through its center. A force of 5.0 N is applied tangentially to the rim. The angular

  4. Physics

    A disk with mass m = 9.8 kg and radius R = 0.31 m begins at rest and accelerates uniformly for t = 18.7 s, to a final angular speed of ω = 31 rad/s. a. What is the angular acceleration of the disk? b. What is the angular

You can view more similar questions or ask a new question.