HES 307 Exam 3 Questions And Answers 100% Correct Review 2024
Tribology - ANS-The science of interacting surfaces in relative motion; not just specific to bearings,
anything where we have to look at interacting surfaces.
Friction - ANS-Any force opposing direction of impending motion due to int...
HES 307 Exam 3 Questions And Answers 100% Correct Review 2024
Tribology - ANS-✔✔The science of interacting surfaces in relative motion; not just specific to bearings,
anything where we have to look at interacting surfaces.
Friction - ANS-✔✔Any force opposing direction of impending motion due to interaction with another
surface.
How are we resolving the interaction force into components? - ANS-✔✔We need to resolve the
interaction force into components normal and tangent to the surface
Traction definition 1 - ANS-✔✔Traction applies when one of the bodies has the ability to develop its
own power while it attempts to gain motion.
(accelerating or deccelerating)
This means we can only use traction when we can develop power. Examples are a braking force
generation on the sport surface by an athlete.
We have a breaking or slowing aspect therefore in this definition it can be use to replace the friction
definition.
Traction Definition 2 - ANS-✔✔Traction is used in place of friction what classic laws of friction do not
apply
Classic Friction can also be called: - ANS-✔✔1. Coulomb Friction or Dry Friction
Friction force is dependent on: - ANS-✔✔1.Properities of both objects and how they interact
(smoothness/roughness)
2. Normal force between the objects (perpendicular)
,3. If relative motion (sliding) exists
No motion is:
Relative motion or sliding is: - ANS-✔✔static friction
dynamic friction (kinetic)
Classic friction is independent of: - ANS-✔✔contact area and the velocity of sliding (how fast the object
is sliding will not affect the friction force .
Classic friction assumes no - ANS-✔✔Deformation (rigidness does not make a difference)
Adhesion (no chemical stickiness inhibiting motion to occur)
One of the static equations for friction can help us determine: - ANS-✔✔What the maximum force from
friction will be under static conditions.
Created between the surfaces of interaction before sliding will begin to occur.
As soon as you push harder static friction will break and start to slide.
What happens if our horizontal forces exceed the FsFMax value? - ANS-✔✔We slide! Now we have
dynamic friction conditions and we have a new coefficient of friction!
What happens to dynamic friction when we increase the speed of the sliding? - ANS-✔✔Nothing!
Dynamic friction is independent of how fast it is sliding. We will generate the same amount of friction
force.
When will dynamic sliding conditions stop? - ANS-✔✔It will stop sliding when the applied force is LESS
than Fdf (dynamic friction force)
, The coefficient of dynamic frictions is _______ than the coefficient of static friction - ANS-✔✔less.
It will take a larger force to get it to start sliding than it will to have it keep sliding once it is moving.
According to Coulomb friction conditions all coefficients of friction need to be: - ANS-✔✔less than 1
True or False: Normal force is always the weight of the object - ANS-✔✔False!
How to we maintain traction?
Come up with an example. - ANS-✔✔Need to keep the ration of (GRFx/GRFy) < Us
Ex: (GRFx/GRFy) = .7 and Us = .9 you're safe from sliding!
The higher your COF (max ration during the stance phase): - ANS-✔✔the more likely you are to slip.
When are your greatest risks for slipping? - ANS-✔✔Early on and late in the motion. Not much risk od
slipping mid stance
This is due to the ratio of (GRFx/GRFy) being low and less than the COF
Is sliding easier when the normal force is high or low? - ANS-✔✔The greater the normal force, the
harder it is to slide because the friction force is greater.
Increase in normal force = increase in friction force
Increase in friction force =. decrease in ability to slide
On inclines what forces should you consider? - ANS-✔✔Normal forces and forces tangent to the
surface.
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