Everyday Forces Holt Physics Chapter 4 Section 4 Pages 141-148.
-
Upload
ross-marshall -
Category
Documents
-
view
261 -
download
4
Transcript of Everyday Forces Holt Physics Chapter 4 Section 4 Pages 141-148.
Everyday Forces Everyday Forces Holt PhysicsHolt Physics
Chapter 4 Section 4Chapter 4 Section 4
Pages 141-148Pages 141-148
Everyday Forces Everyday Forces
WeightWeight – the magnitude of the force – the magnitude of the force of gravity acting on an objectof gravity acting on an object
Everyday Forces Everyday Forces
FFgg = mg = mgFFgg = force due to gravity (in Newtons) = force due to gravity (in Newtons)
m = mass of object (in kilograms)m = mass of object (in kilograms)
g = acceleration due to gravity (-9.81 m/sg = acceleration due to gravity (-9.81 m/s22))
* Mass ≠ Weight* Mass ≠ Weight
Everyday Forces Everyday Forces
Normal ForceNormal Force – (F – (Fnn) – a contact force ) – a contact force exerted by one object on another in exerted by one object on another in a direction perpendicular to the a direction perpendicular to the surface of contact. On a horizontal surface of contact. On a horizontal surface, Fsurface, Fnn = mg = mg
Everyday Forces Everyday Forces
Normal force diagrams- Normal force diagrams-
Everyday Forces Everyday Forces
Frictional Forces – Contact forces which Frictional Forces – Contact forces which oppose applied forcesoppose applied forces
These are the surfaces in contact at a These are the surfaces in contact at a microscopic level.microscopic level.
Everyday ForcesEveryday Forces1. Static friction - (Fs) - force exerted1. Static friction - (Fs) - force exerted
on a motionless object by theon a motionless object by the
environment to environment to
resist an resist an
external force external force
attempting to attempting to
cause a change cause a change
in motionin motion
Everyday ForcesEveryday Forces2. Kinetic friction – (Fk) – force2. Kinetic friction – (Fk) – force
exerted on a moving object thatexerted on a moving object that
opposes opposes
motionmotion
Everyday ForcesEveryday Forces * Fk < Fs due to surface adhesion * Fk < Fs due to surface adhesion
between two surfaces in contactbetween two surfaces in contact Coefficient of friction (μ) – a ratio of Coefficient of friction (μ) – a ratio of
frictional force to normal force frictional force to normal force between two objectsbetween two objects
Coefficient of FrictionCoefficient of Friction
The coefficient of friction is a ratio of The coefficient of friction is a ratio of force of friction to the normal force force of friction to the normal force acting between two objects.acting between two objects.
This completely depends on the This completely depends on the objects in contact.objects in contact.
Different experimental values have Different experimental values have been calculated based on the been calculated based on the materials in contact materials in contact (page 144: table 4-2)(page 144: table 4-2)
Coefficient of Friction EquationsCoefficient of Friction Equations
Coefficient of static frictionCoefficient of static friction
μμss = = FFs,maxs,max
FFnn
Coefficient of kinetic frictionCoefficient of kinetic friction
μμkk = = FFkk
FFnn
Everyday ForcesEveryday Forces
3. Air resistance is 3. Air resistance is
a form of friction a form of friction
as velocity as velocity
increases so does increases so does
air resistanceair resistance