Motion of a Sphere: No Friction vs With Friction

  • Thread starter Thread starter chaoseverlasting
  • Start date Start date
  • Tags Tags
    Motion Sphere
Click For Summary

Homework Help Overview

The discussion revolves around the motion of a sphere on a horizontal surface when a force is applied, specifically comparing scenarios with and without friction. Participants are exploring the implications of friction on the sphere's motion, including translational and rotational aspects.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the nature of motion without friction as purely translational, while questioning how friction introduces rotational motion. There is debate about whether the applied force can create torque and the role of friction in this context.

Discussion Status

The discussion is active, with participants offering differing perspectives on the effects of friction and torque. Some express confusion regarding the textbook's stance on rotational motion, indicating a lack of consensus on the interpretation of the problem.

Contextual Notes

There is mention of a textbook that states there can be no rotational motion under any conditions, which some participants are questioning. This suggests a potential discrepancy between the problem setup and the provided educational material.

chaoseverlasting
Messages
1,051
Reaction score
3

Homework Statement


A sphere is resting on a horizontal surface. A force parallel to the surface passing through the center of the sphere is applied.

Describe the motion of the sphere
1. Without any friction
2. With friction.



The Attempt at a Solution



When there's no friction, then the motion is purely translatory. But, if there is friction, it will apply a torque which will force rotation as well as translation. The second part isn't right though. Why?
 
Physics news on Phys.org
It cannot apply any torque, because the force goes right through the center of the sphere. What happens is that the friction touching the ball below is the culprit in creating this invisible torque.
 
The force initially applied does not have any torques but it is the friction itself that acts as a torque that rotates the ball equivalent to (frictional force*radius of the sphere)
 
Yeah, that's what I thought, but the book says that there can be no rotational motion under any conditions. I thought the book was wrong but maybe I'd missed something.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 97 ·
4
Replies
97
Views
6K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 35 ·
2
Replies
35
Views
5K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
24
Views
3K
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
1K