What conditions are needed so that a billiard ball slides rather than rotates?

In summary, the conversation is discussing the factors that contribute to a ball's rotation, including sliding friction, moment of inertia, and the relationship between these forces and equations. The participants also discuss the concept of torque and its role in causing and opposing rotational movement. They question the validity of equating different equations and discuss the dimensions and connections between different variables in rotational motion.
  • #1
great_sushi
30
0
Or at the point at which it starts to rotate...

My thinking is that the sliding friction is the only thing that will cause the ball to rotate F = u*N
N = mg

And moment of inertia I = 2/5*m*r^2

So, when I = 2/5*m*r^2 = u*N = F it will be at the instant of the change over...

Am i right in thinking that??
 
Physics news on Phys.org
  • #2
As far as I know it's the static friction which causes moment and makes the ball roll.
 
  • #3
OK static friction. Am I right in equating the two equations?
 
  • #4
great_sushi said:
OK static friction. Am I right in equating the two equations?
Well, how did you get it? It doesn't make sense to me.
 
Last edited:
  • #5
Well, if the table was frictionless and if you hit the ball dead center it would never rotate...

So the frictional force will be the force that causes the rotation...

The sliding will occur if something opposes the frictional force... ie the mass moment of inertia of the ball.

If the frictional force is equivalent to the mass moment of inertia then the ball won't rotate. Right?
 
  • #6
The moment of inertia is a property of an object and it resists angular acceleration cf. mass in linear motion. It is neither a force nor moment. Right? :smile:
 
  • #7
OK so I'm wrong. Can you point me in the right direction then?
 
  • #8
great_sushi said:
So, when I = 2/5*m*r^2 = u*N = F it will be at the instant of the change over...
Take a look at the dimensions (M, L, T, ...). I = ML2, F = MLT-2. So the equation cannot make sense.
What torque does the frictional force exert about the ball's centre?
What kind of movement results from an unopposed torque?
What equation connects that movement with the torque and the moment of inertia?
 

FAQ: What conditions are needed so that a billiard ball slides rather than rotates?

1. What is friction and how does it affect the movement of a billiard ball?

Friction is the force that opposes the sliding or rolling motion of an object. In the case of a billiard ball, friction between the ball and the table will determine whether it slides or rotates.

2. What surface conditions are needed to ensure that a billiard ball slides rather than rotates?

The surface of the billiard table should be smooth and free from any obstacles or imperfections. Additionally, it should be clean and dry to minimize the amount of friction between the ball and the table.

3. How does the weight and size of a billiard ball impact its movement?

The weight and size of a billiard ball can affect its movement by influencing the amount of friction between the ball and the table. A heavier and larger ball will have more surface area in contact with the table, resulting in more friction and a slower sliding motion.

4. What role does the initial velocity of the billiard ball play in determining whether it slides or rotates?

The initial velocity of the billiard ball can determine whether it slides or rotates by affecting the amount of force and energy that is transferred to the ball upon impact with the cue stick. A higher initial velocity will result in a greater amount of energy being transferred, potentially causing the ball to rotate instead of slide.

5. Can external factors such as air resistance or humidity impact the movement of a billiard ball?

External factors such as air resistance or humidity can have a minor impact on the movement of a billiard ball. However, the effect is usually negligible and does not significantly alter the sliding or rotating motion of the ball.

Similar threads

Horizontal impulse on a ball at rest on a plane (with friction)
Replies
14
Views
2K
Friction Required for Billiard Ball to Roll without Slipping
2
Replies
60
Views
1K
Spherical ball rolling back and forth in a bowl
Replies
24
Views
503
How Do You Calculate the Ratio h/R for a Spinning Billiard Ball?
Replies
3
Views
2K
Derive the period of a Ball rolling in a Bowl
Replies
28
Views
2K
Wooden sphere rolling on a double metal track
3
Replies
97
Views
4K
Mechanics: A bowling ball is thrown and rolls with slipping
Replies
8
Views
3K
Conservation of energy problem: Ball rolling down inclined plane and then through a loop-the-loop
Replies
10
Views
1K
Ball rolling in a magnetic field
Replies
2
Views
1K
The normal force on a thin stick being lifted on a surface
3
Replies
95
Views
5K

Hot Threads

Recent Insights

Back
Top