Direction of damping force on a surface

In summary, there is a frictional force acting on a particle bouncing on a surface with a viscous damping coefficient, which is perpendicular to the surface and decreases with an angle of cos(theta) if there is no surface friction. This force can be measured using velocity or other means such as a tensometer, and cannot be expressed solely in terms of gravity. The force exerted by the surface at the point of collision is not damped by a factor of (1-c) and there is no other way for the damping coefficient to affect the force exerted on the particle during collision.
  • #1
kakarot1905
18
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
 
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  • #2
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.
 
  • #3
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?
 
  • #4
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)
 
  • #5
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?
 
  • #6
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
 
  • #7
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))?
 
  • #8
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?
 
  • #9
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
 

1. What is damping force on a surface?

Damping force on a surface is a force that opposes the motion of an object on that surface. It is caused by the friction between the object and the surface, and it reduces the amplitude of the object's oscillations.

2. How does the direction of damping force affect the motion of an object?

The direction of damping force determines whether the object's motion will be slowed down or sped up. If the damping force is in the opposite direction of the object's motion, it will slow down the object. If the damping force is in the same direction as the object's motion, it will speed up the object.

3. What factors affect the direction of damping force on a surface?

The direction of damping force is affected by the type of surface the object is moving on, the weight of the object, and the speed of the object's motion. In general, rougher surfaces and heavier objects will have a greater damping force in the opposite direction of the object's motion.

4. How can the direction of damping force be changed?

The direction of damping force can be changed by altering the surface properties, such as making the surface smoother or rougher. Additionally, changing the weight or speed of the object can also affect the direction of damping force.

5. Is damping force always present on a surface?

No, damping force is not always present on a surface. It depends on the type of surface and the conditions of the object's motion. For example, on a smooth surface with low friction, there may be very little or no damping force present.

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