Motion in a plane II, Coin on a turntable with Vmax

Click For Summary

Homework Help Overview

The problem involves a coin placed on a turntable, where the objective is to determine the maximum angular velocity at which the turntable can spin without the coin sliding off. The scenario includes parameters such as the mass of the coin, the distance from the center of the turntable, and the coefficients of friction.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss drawing free body diagrams to analyze the forces acting on the coin. There are questions about the direction of forces and how they interact, particularly concerning the normal force, gravitational force, and frictional force. Some participants attempt calculations for maximum speed and angular velocity, while others express uncertainty about the relevance of their equations.

Discussion Status

The discussion includes various attempts to clarify the forces involved and their balance at the point of impending motion. Some participants have provided calculations for maximum speed and angular velocity, with indications of progress in understanding the problem. However, there is no explicit consensus on the final approach or solution.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. There is an emphasis on understanding the forces involved without providing complete solutions.

SherBear
Messages
81
Reaction score
0

Homework Statement



A 3.90 g coin is placed 12.0cm from the center of a turntable. The coin has static and kinetic coefficients of friction with the turntable surface of Ws= 0.800 and Wk= 0.410.

What is the maximum angular velocity with which the turntable can spin without the coin sliding?



Homework Equations


?



The Attempt at a Solution


? no idea
can you please show all the steps and the solution, thank you!
 
Physics news on Phys.org
Draw a free body diagram of the coin showing all forces. Then look at the forces and determine how they interact with one another.
 
LawrenceC said:
Draw a free body diagram of the coin showing all forces. Then look at the forces and determine how they interact with one another.

Does a turntable turn clockwise? Normal force up, mg down, Ff opposite of the motion if clockwise then it's counterclock wise?

I have Vmax=SQRT Ws r g=SQRT .800*.12m*9.81 m/s^2= .938 m/s, but I don't know if that's a relevant equation.

Then I have an equation for angular velocity=Vt=wr
 
SherBear said:
Does a turntable turn clockwise? Normal force up, mg down, Ff opposite of the motion if clockwise then it's counterclock wise?



The turntable is turning at constant speed so you are not concerned with tangential force here. We want to determine what the maximum speed is.

At the point of impending coin movement outward, what forces are exactly balanced?
 
"I have Vmax=SQRT Ws r g=SQRT .800*.12m*9.81 m/s^2= .938 m/s"

Use parentheses.

Your calculator seems to cause problems.

I am signing off for the day. You are on the right track.

Angular velocity = V/r
 
Last edited:
LawrenceC said:
The turntable is turning at constant speed so you are not concerned with tangential force here. We want to determine what the maximum speed is.

At the point of impending coin movement outward, what forces are exactly balanced?

I think the normal force and gravitational forced are the balanced forces.
 
ok i did the calc with para, and the result was Vmax=.9704 m/s
then i plugged that into the m=v/r
.9704 m/s / .12 m = 8.09 rad/s ?
 
That is what I calculated. Good work.
 
Thank you Lawrence! and for all your help and hardwork also! :)
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
3
Views
2K
Replies
1
Views
2K
Replies
2
Views
2K
Replies
4
Views
5K
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
5K