Direction of damping force on a surface

Click For Summary

Discussion Overview

The discussion revolves around the nature of the damping force experienced by a particle bouncing on a surface, particularly focusing on its direction and dependence on various factors such as velocity and surface angle. Participants explore theoretical aspects of damping in both vertical and tilted scenarios, as well as methods for measuring damping force.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the frictional force due to damping is directed perpendicular to the surface when the particle hits it perpendicularly.
  • Others argue that when a particle interacts with a tilted surface, the damping force is influenced by the velocity component perpendicular to the surface, alongside other forces such as parallel friction and rotational energy transfer.
  • There is a suggestion that damping force could be expressed in terms of gravitational force at the point of impact, but some participants assert that this is not feasible since damping depends on velocity.
  • One participant questions whether the damping force decreases by a factor related to the cosine of the angle of the surface, to which others agree under certain conditions.
  • Participants discuss alternative methods for measuring damping force, such as using a tensometer or piezoelement, while noting that measuring velocity is the simplest approach for home experiments.
  • A question is raised about whether the force exerted by the surface at the point of collision can be described as damped by a factor involving the viscous damping coefficient, which is met with skepticism from others.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the direction and expression of the damping force, as well as its dependence on velocity and surface angle. The discussion remains unresolved on several points, particularly regarding the relationship between damping and gravitational force.

Contextual Notes

Participants highlight the complexity of the damping force's behavior based on the angle of the surface and the velocity of the particle, indicating that assumptions about surface friction and rotational effects may limit their conclusions.

kakarot1905
Messages
17
Reaction score
0
Hi

Suppose a particle is bouncing on a surface with a viscous damping coefficient...

Question 1:
The frictional force = -c(viscous damping coefficient)*v(velocity of the particle)

But what is the direction of this force?
Perpendicular [down] to surface?

So if the surface is tilted at an angle what would the frictional force be?

Question 2:
Is it possible to express frictional force [due to damping] using force due to gravity (on the point of impact) and not velocity?

Thanks
 
Physics news on Phys.org
kakarot1905 said:
But what is the direction of this force?
Perpendicular [down] to surface?
Yes.

So if the surface is tilted at an angle what would the frictional force be?
if your ball hits the surface perpendicularly - the force is as you wrote.
But if you just drop a ball on tilted surface, or throw it at any other angle, you will have combined effect of damping friction (depending on velocity component perpendicular to the surface), friction in motion parallel to the surface, and energy transfer to rotation of your ball.

Is it possible to express frictional force [due to damping] using force due to gravity (on the point of impact) and not velocity?
Nope. Just take extreme case: if you lay your ball on a table (velocity is 0) there is no dumping friction, but gravity is always the same.
 
xts said:
Yes.


if your ball hits the surface perpendicularly - the force is as you wrote.
But if you just drop a ball on tilted surface, or throw it at any other angle, you will have combined effect of damping friction (depending on velocity component perpendicular to the surface), friction in motion parallel to the surface, and energy transfer to rotation of your ball.

Is it possible to express frictional force [due to damping] using force due to gravity (on the point of impact) and not velocity?
Nope. Just take extreme case: if you lay your ball on a table (velocity is 0) there is no dumping friction, but gravity is always the same.


About the angled surface... Ignoring the surface friction, would the damping force decrease by an angle of cos(theta) or something like that?
 
About the angled surface... Ignoring the surface friction, would the damping force decrease by an angle of cos(theta) or something like that?
Yes, if you are not interested in rotation nor forces parallel to the surface, then damping friction depends on perpendicular component of the velocity - or, if you prefer, on speed*cos(theta)
 
xts said:
Yes, if you are not interested in rotation nor forces parallel to the surface, then damping friction depends on perpendicular component of the velocity - or, if you prefer, on speed*cos(theta)

Thanks for all the replies xts..

Do you know any other means of measuring the damping force [by the surface on the particle] other than using velocity?
 
You may use tensometer, or some kind of scale: eg a light plate glued on piezoelement, but velocity seems to be definitely the simplest and most feasible for no-budget home experiment
 
xts said:
You may use tensometer, or some kind of scale: eg a light plate glued on piezoelement, but velocity seems to be definitely the simplest and most feasible for no-budget home experiment

Thanks :)

One last question:
The force exerted by the plate at point of collision...
Is is it ok to say this force is damped by a factor (1–(c))?
 
kakarot1905 said:
The force exerted by the plate at point of collision...
Is is it ok to say this force is damped by a factor (1–(c))?
Oooch?
It definitely is wrong, I wonder why do you think so?
 
xts said:
Oooch?
It definitely is wrong, I wonder why do you think so?

Ok, is there any other possible way, the viscous damping coefficient [or the damping nature of the surface] affect the force exerted on the particle during its collision
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 20 ·
Replies
20
Views
5K
  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 25 ·
Replies
25
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 35 ·
2
Replies
35
Views
5K