Will a rolling ball ever stop?

In summary, the textbook solution for a pipe rolling down an incline takes into account only gravity and assumes zero friction. This means that on a level surface with only gravity as the force, the object will not accelerate or decelerate. However, in real situations, friction and other forces like surface hardness and drag play a role in slowing down the object. The textbook model is an idealized one and may not be applicable to real-world scenarios where friction and other forces are present. Additionally, the assumption of a single point of contact with the ground may not be accurate, leading to a restoring torque that slows down the object.
  • #1
Euclid
214
0
The textbook solution for a pipe rolling down an incline is [tex]a = \frac{1}{2} g \sin \theta [/tex]. Putting in theta = 0 gives a = 0. Does this imply that a ball rolling along a level surface will never stop?
 
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  • #2
It means that the object will not accelerate on a level plane if gravity is the only force.
 
  • #3
Gravity is not the only force on an incline. Friction acts as well. And friction acts on a level plane too. So a rolling ball should come to a stop due to friction...
 
  • #4
the textbook solution was for an "idealized model" with zero friction.
The MODEL has zero friction. Your fault if you try to apply this model
to situations where friction is NOT ignorable.

You're right, the model has a (hard) surface's Force as well as gravity's Force. And it suggests that the pipe rolling on a level floor will not slow down. Don't try this a home ; you'll soon over-reach this model when the pipe hits the kitchen table.
 
  • #5
You said that this is the formula for a pipe rolling. If it was sliding, then friction would be a problem, but as it is rolling, friction shouldn't be the problem should it?
If I'm right, then the error would be due to some of the kinetic energy of motion being converted to heat, due to the particles of the pipe hitting against the particles in the surface when it is rolling, and drag.
So the textbook model was from an idealised model with friction, but with no energy loss as heat or drag.
 
  • #6
There is also the fact that, it is not exactly one point that touches the ground during rolling motion as we assume in the ideal case. There will be an area which is in contact with the ground. Due to this the Normal force does not pass exactly through the center and hence there's a restoring torque which slows down the pipe.
 

1. Will a rolling ball ever stop?

The answer to this question depends on a few factors. If the ball is rolling on a surface with no friction, it will continue to roll forever. However, in the real world, there is always some friction present, so the ball will eventually come to a stop.

2. What factors affect how long a rolling ball will continue to roll?

The main factors that affect how long a rolling ball will continue to roll are the surface it is rolling on and the initial force or energy applied to the ball. A smoother surface with less friction will allow the ball to roll for longer, while a rougher surface with more friction will cause the ball to stop sooner. Additionally, the more force or energy applied to the ball, the longer it will continue to roll.

3. Can a rolling ball ever roll indefinitely without stopping?

No, it is not possible for a rolling ball to continue rolling indefinitely without some external force or energy being applied. As mentioned before, even on a surface with minimal friction, there is still some resistance present that will eventually cause the ball to stop. In order for the ball to continue rolling, a continuous source of energy would need to be applied.

4. What is the role of gravity in a rolling ball coming to a stop?

Gravity does play a role in a rolling ball coming to a stop, but it is not the main factor. Gravity helps to accelerate the ball as it rolls downhill, but it also creates resistance that slows down the ball as it rolls uphill. Ultimately, it is the friction between the ball and the surface it is rolling on that causes it to come to a stop.

5. How does the shape of a rolling ball affect its ability to continue rolling?

The shape of a rolling ball can affect its ability to continue rolling in a few ways. A perfectly round ball will roll more smoothly and have less friction compared to a ball with an irregular shape. Additionally, a ball with a larger diameter will have more rotational inertia, making it more difficult to stop compared to a smaller ball with less rotational inertia.

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