Moment of a rod of varying thickness

Click For Summary

Homework Help Overview

The problem involves a cylindrical steel shaft with varying radius, specifically a transition from a radius of 2 cm to 1 cm over a distance of 20 cm. The task is to determine the distance of the center of gravity from the thicker end of the shaft.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the interpretation of the problem, particularly regarding the dimensions and the setup of the shaft. There are inquiries about the mass calculation and the role of density in the context of the problem.

Discussion Status

Some participants have provided guidance on how to approach the problem, suggesting the calculation of mass for each section of the shaft and the use of the center of mass formula. There is ongoing clarification regarding the problem statement and its parameters.

Contextual Notes

There are mentions of potential confusion due to the phrasing of the problem, and participants are encouraged to clarify the original question as it appears in their textbook.

lordsnowbrood
Messages
8
Reaction score
0

Homework Statement



Q A cylindrical steel shaft of radius 2cm and long is turned upside down on a lathe to one half its radius for a distance of 20cm from one end find the distance of its centre of gravity from the thicker end.?

Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org


lordsnowbrood said:

Homework Statement



Q A cylindrical steel shaft of radius 2cm and long is turned upside down on a lathe to one half its radius for a distance of 20cm from one end find the distance of its centre of gravity from the thicker end.?

Homework Equations




anticlockwise moment=clockwise moment

The Attempt at a Solution

i don't get the question so can anyone help solve this
 


Hey,
Welcome to PF.

In the second line, is there a typing mistake?

I think you have not copied the question in its exact language , which is causing some confusion (especially the grammar.)

Can you retype it?
 
welcome to pf!

hi lordsnowbrood! welcome to pf! :smile:
lordsnowbrood said:
Q A cylindrical steel shaft of radius 2cm and long is turned upside down on a lathe to one half its radius for a distance of 20cm from one end find the distance of its centre of gravity from the thicker end.?

(you missed out the length … let's call it L :wink:)

do you mean that it has radius 2 cm for length L - 20 cm, and radius 1 cm for length 20 cm ?

if so, find the mass of each part, pretend it's concentrated at the centre of mass (of that part), and then use the usual formula for two masses :smile:
 


tiny-tim said:
hi lordsnowbrood! welcome to pf! :smile:


(you missed out the length … let's call it L :wink:)

do you mean that it has radius 2 cm for length L - 20 cm, and radius 1 cm for length 20 cm ?

if so, find the mass of each part, pretend it's concentrated at the centre of mass (of that part), and then use the usual formula for two masses :smile:

yes you are right.. but how to find mass??
 
Last edited by a moderator:


emailanmol said:
Hey,
Welcome to PF.

In the second line, is there a typing mistake?

I think you have not copied the question in its exact language , which is causing some confusion (especially the grammar.)

Can you retype it?

no mistakes buddy i copied it from my book Abbott physics
 
lordsnowbrood said:
yes u are right.. but how to find mass??

call the density "ρ" … it'll cancel out at the end :smile:
 


lordsnowbrood said:
no mistakes buddy i copied it from my book Abbott physics

Wow! That must be Physics by Abbott and Costello then :smile:
 


I think you have not copied the question in its exact language , which is causing some confusion (especially the grammar.)
Can you retype it?
GRAMMAR
 
  • #10
lordsnowbrood said:

Homework Statement



Q A cylindrical steel shaft of radius 2cm and 50cm long is turned upside down on a lathe to one half its radius for a distance of 20cm from one end find the distance of its centre of gravity from the thicker end.?

Homework Equations





The Attempt at a Solution

i have made the changes can anyone now solve it
 
  • #11


gneill said:
Wow! That must be Physics by Abbott and Costello then :smile:
well it is a blue book published by heinemann and the author is abbott only
 
  • #12
hi lordsnowbrood! :smile:
lordsnowbrood said:
i have made the changes can anyone now solve it

yes, you can solve it! :wink:

find the mass of each part, pretend it's concentrated at the centre of mass (of that part), and then use the usual formula for two masses …

show us what you get :smile:​
 
  • #13
tiny-tim said:
hi lordsnowbrood! :smile:


yes, you can solve it! :wink:

find the mass of each part, pretend it's concentrated at the centre of mass (of that part), and then use the usual formula for two masses …

show us what you get :smile:​

how could i find the mass man ?? can u help me with that i can find volume but how to find mass in such question got no clue buddy
 
  • #14
lordsnowbrood said:
how could i find the mass man ?? can u help me with that i can find volume but how to find mass …

call the density "ρ" … it'll cancel out at the end :smile:
 
  • #15
tiny-tim said:
call the density "ρ" … it'll cancel out at the end :smile:

could u please solve it coz i cant?
 
  • #16
general strategy: write out the general formula first, then write it out again with the numbers in

(that's why the homework template has that section on Equations! :wink:)​

sooo …

i] what is the general formula for the volume of a cylinder?

ii] what are the volumes of these two cyliners?

iii] what are the positions of their centres of mass (from the end of the large cyiinder)?

iv] multiply by ρ to get the masses

v] what is the general formula of the position of the centre of mass of two masses?

vi] apply that formula (ρ will cancel) :smile:
 

Similar threads

Moment of Inertia in Planet System
  • · Replies 9 ·
Replies
9
Views
2K
Moment of Inertia of rod on an axis
  • · Replies 4 ·
Replies
4
Views
11K
Moment of Inertia question (dead simple)
  • · Replies 3 ·
Replies
3
Views
2K
Centre of mass of non-uniform rod
  • · Replies 8 ·
Replies
8
Views
3K
Two wheels rotating connected by a rod
  • · Replies 26 ·
Replies
26
Views
6K
Uniform rotating rod about a point at one end of the rod
  • · Replies 3 ·
Replies
3
Views
3K
Moment of Torque; Am I solving this correctly?
  • · Replies 3 ·
Replies
3
Views
4K
What Determines Electric Field Strengths of Two Charged Rods
  • · Replies 3 ·
Replies
3
Views
2K
Rotating rod returning to its initial position
  • · Replies 5 ·
Replies
5
Views
1K
Understanding Moment of Inertia in a Ball-Rod System
  • · Replies 1 ·
Replies
1
Views
2K