B Question about a Rotor Ride in a amusement park

  • B
  • Thread starter Thread starter bonbon1
  • Start date Start date
  • Tags Tags
    Rotor
AI Thread Summary
The discussion centers on the concept of static friction, particularly its maximum value when an object is on the verge of sliding. The maximum static friction force is proportional to the normal force, represented mathematically as f_s^{max} = μ_sN. When a person in a rotor experiences changes in angular velocity, the normal force alters, affecting the maximum static friction force accordingly. If the rotor speeds up, the normal force increases, raising the maximum static friction, while slowing down decreases it, potentially leading to slipping if the required friction exceeds the maximum. This explanation clarifies the relationship between normal force, static friction, and motion dynamics.
bonbon1
Messages
4
Reaction score
1
Hi
I don't understand why the static friction force is maximum in this situation?View attachment rotor1.jpg
 
Last edited:
Physics news on Phys.org
Because you are looking for the minimum coefficient of static friction, i.e. the person is just on the verge of sliding.
 
  • Like
Likes bonbon1
kuruman said:
Because you are looking for the minimum coefficient of static friction, i.e. the person is just on the verge of sliding.

ok thank you. Is there also a mathematical explanation for that?
 
bonbon1 said:
ok thank you. Is there also a mathematical explanation for that?
No. There is a mathematical formulation based on a physical event that can be described in plain English. The event is that the person is about to start sliding in which case the force of static friction has reached its maximum value which is proportional to the normal force, the constant of proportionality being the coefficient of static friction. All that wording can be formulated in shorthand mathematical notation as ##f_s^{max}=\mu_sN##. It's a much more compact way of saying the same thing and that's why we use math when we do physics.
 
kuruman said:
No. There is a mathematical formulation based on a physical event that can be described in plain English. The event is that the person is about to start sliding in which case the force of static friction has reached its maximum value which is proportional to the normal force, the constant of proportionality being the coefficient of static friction. All that wording can be formulated in shorthand mathematical notation as ##f_s^{max}=\mu_sN##. It's a much more compact way of saying the same thing and that's why we use math when we do physics.
and if there is a situation in which a person is in a rotor and the angular velocity changes (and then as a result, the normal force changes) and the person is still stucked to the wall, is it affect the fs or just the fsmax?
 
Last edited:
bonbon1 said:
and if there is a situation in which a person is in a rotor and the angular velocity changes (and then as a result, the normal force changes) and the person is still stucked to the wall, is it affect the fs or just the fsmax?
To be clear, we have the person in a rotor and they are just on the verge of sliding down. The force of static friction is exactly equal to the maximum force of static friction. But now the rotor speeds up. The normal force increases.

1. Because the normal force has increased, the maximum possible force from static friction has increased.

2. If it only takes a frictional force of magnitude mg to support the person, it still only takes that much frictional force no matter how fast the rotor spins. The actual frictional force will be only as much as is required, not as much as could possibly be provided.

If, on the other hand the rotor slows down then the normal force decreases.

1. Because the normal force has decreased, the maximum possible force from static friction has decreased.

2. If it takes a frictional force of magnitude mg to support the person and the maximum force of static friction is less than that then the actual force from static friction will be equal to the maximum and the person is doomed to slip downward.
 
Last edited:
  • Like
Likes berkeman and bonbon1
jbriggs444 said:
To be clear, we have the person in a rotor and they are just on the verge of sliding down. The force of static friction is exactly equal to the maximum force of static friction. But now the rotor speeds up. The normal force increases.

1. Because the normal force has increased, the maximum possible force from static friction has increased.

2. If it only takes a frictional force of magnitude mg to support the person, it still only takes that much frictional force no matter how fast the rotor spins. The actual frictional force will be only as much as is required, not as much as could possibly be provided.

If, on the other hand the rotor slows down then the normal force decreases.

1. Because the normal force has decreased, the maximum possible force from static friction has decreased.

2. If it takes a frictional force of magnitude mg to support the person and the maximum force of static friction is less than that then the actual force from static friction will be equal to the maximum and the person is doomed to slip downward.
Thank you! Now I understand
 
  • Like
Likes berkeman

Similar threads

Replies
8
Views
914
Replies
3
Views
2K
Replies
3
Views
1K
Replies
2
Views
2K
Replies
59
Views
4K
Replies
251
Views
7K
Back
Top