Understanding Rolling Without Slipping

In summary, when an object is rolling without slipping on a rough, flat surface, there is a net torque provided by friction at the contact point. However, once the "rolling without slipping" condition is met, there is no longer friction acting and no net torque. This is possible because friction is only needed to change the speed of the object, and once the object is moving at the right speed to prevent slipping, friction is no longer necessary. On a sloped surface, friction is needed to increase the rotational speed of the object to maintain the no-slip condition.
  • #1
Conservation
63
0
For conditions where an object is rolling without slipping on a rough, flat surface, the object posses a net torque about the center of mass provided by friction at the contact point. Hence, why doesn't the object accelerate radially indefinitely?

For ex, if we had a slippery bowling ball rolling down a rough, flat surface, its radial acceleration would increase until its translational velocity=W*R (no-slip condition met) and then continue to do so. Why does the radial acceleration no longer occur despite the presence of a net torque?
 
Physics news on Phys.org
  • #2
Conservation said:
For conditions where an object is rolling without slipping on a rough, flat surface, the object posses a net torque about the center of mass provided by friction at the contact point. Hence, why doesn't the object accelerate radially indefinitely?
If the surface is horizontal, there would be no static friction and thus no torque. (Ignoring details like rolling resistance.) If it's rolling downhill, then it would keep accelerating.

Conservation said:
For ex, if we had a slippery bowling ball rolling down a rough, flat surface, its radial acceleration would increase until its translational velocity=W*R (no-slip condition met) and then continue to do so. Why does the radial acceleration no longer occur despite the presence of a net torque?
Once the "rolling without slipping" condition is met, there is no longer friction acting and no net torque. At least for a horizontal surface.
 
  • #3
Why is there friction for a sloped surface and no friction for a flat surface?
 
  • #4
Conservation said:
Why is there friction for a sloped surface and no friction for a flat surface?
Friction acts to prevent slipping between surfaces. For a horizontal surface, friction is not need to prevent slipping. Friction is needed for a sloped surface.
 
  • #5
I'm sorry, but I don't follow. It's definitely possible to have an object slip or slip/roll on a horizontal surface, and friction is present for those cases...
 
  • #6
Conservation said:
I'm sorry, but I don't follow. It's definitely possible to have an object slip or slip/roll on a horizontal surface, and friction is present for those cases...
Only if it's accelerating. Once it meets the no-slip condition, you can change the surface to one that is perfectly frictionless and you won't know the difference. Friction is only needed to change the speed (rotational and translational).
 
  • #7
So friction exists before no-slip condition and then becomes 0 once it reaches no-slip? That makes sense logically and satisfies the lack of net torque in rolling without slipping, but I don't see how this is physically possible.
 
  • #8
Conservation said:
So friction exists before no-slip condition and then becomes 0 once it reaches no-slip?
Right.

Conservation said:
That makes sense logically and satisfies the lack of net torque in rolling without slipping, but I don't see how this is physically possible.
Imagine the surface suddenly became frictionless as the object rolled along. What would be the relative speed of the bottom surface of the object and the frictionless surface? Would there be slipping? (Remember, we are talking about static friction here.)
 
  • #9
Relative speed would be 0, which makes the friction static. But shouldn't the static friction still have some form of direction, providing net torque?
 
  • #10
Conservation said:
Relative speed would be 0, which makes the friction static.
Since (without friction) there is no slipping (as you said, the relative speed is zero), friction is not needed to prevent it. Only if there would be slipping without the friction, would you need friction.

Conservation said:
But shouldn't the static friction still have some form of direction, providing net torque?
The static friction is zero, since it's moving at just the right speed so there is no slipping to prevent.
 
  • #11
Okay, I think I understand now for the scenario of the flat surface. Thank you.
What about sloped surface, though? Why would rolling without slipping on a sloped surface have friction?
 
  • #12
Conservation said:
Okay, I think I understand now for the scenario of the flat surface. Thank you.
Cool.

Conservation said:
What about sloped surface, though? Why would rolling without slipping on a sloped surface have friction?
Since the object is speeding up, the rotational speed must increase accordingly to maintain no slipping. That requires friction exerting a torque.
 
  • Like
Likes jbriggs444

Related to Understanding Rolling Without Slipping

1. What is rolling without slipping?

Rolling without slipping is a type of motion in which an object, such as a wheel, rotates while also translating without any slipping or sliding. This means that the point of contact between the object and the surface it is rolling on remains stationary.

2. What causes an object to roll without slipping?

An object rolls without slipping when there is sufficient friction between its rolling surface and the surface it is rolling on. This friction allows the object to both rotate and translate without slipping. Additionally, the shape and distribution of mass of the object also play a role in its ability to roll without slipping.

3. How is rolling without slipping different from sliding?

Rolling without slipping is different from sliding in that the point of contact between the object and the surface remains stationary in rolling without slipping, whereas in sliding, the object moves and slides along the surface. Rolling without slipping also requires a combination of both translational and rotational motion, while sliding only involves translational motion.

4. Can an object roll without slipping on any surface?

No, an object cannot roll without slipping on any surface. The surface must have enough friction to prevent slipping, and the object must also have the appropriate shape and mass distribution to allow for rolling without slipping. For example, a ball can roll without slipping on a rough surface, but a hockey puck will slide instead of roll on the same surface.

5. What are some real-world examples of rolling without slipping?

Some common examples of rolling without slipping include a car's tires rolling on the road, a bicycle wheel rolling on the ground, and a ball rolling on a court or field. Additionally, many machines and mechanisms, such as gears and pulleys, rely on rolling without slipping to function properly.

Similar threads

I Friction in rolling without slipping
    • Mechanics
Replies
7
Views
2K
B Rolling without slipping in non-sloping surface
    • Mechanics
Replies
13
Views
1K
Rolling without slipping down an inclined plane
    • Mechanics
2
Replies
41
Views
4K
B Rolling of non-deforming sphere on a non-deforming rough surface?
    • Mechanics
Replies
4
Views
917
B Why is static friction necessary for pure rolling?
    • Mechanics
Replies
4
Views
1K
Rolling with slipping and conditions for not slipping
    • Mechanics
Replies
7
Views
2K
Rolling Without Slipping: What Am I Missing?
    • Mechanics
2
Replies
52
Views
5K
Question regarding Rolling with and without Slipping and Sliding
    • Introductory Physics Homework Help
Replies
4
Views
1K
Rolling without Slipping - axes of rotation and centripital acceleration
    • Mechanics
Replies
1
Views
1K
B Friction on pure rolling non deforming sphere?
    • Mechanics
Replies
3
Views
1K

Hot Threads

Recent Insights

Back
Top