Download Which of Newton`s Three Laws does the following statement satisfy?

Wednesday January 14
Hand-in Todays Homework
• Page 139
• Page 144-145
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1-4
23-29
We will look at friction, air resistance.
Open book quiz.
Review and in class problems on Friday
Test on Monday
Review: Newton’s Laws
Let’s review Newton’s three laws together
Which of Newton's Three Laws does the
following statement satisfy?
The relationship between an object's mass (m),
its acceleration (a), and the applied force F is
F=ma. Acceleration and force are vectors. This
law requires that the direction of the
acceleration vector is in the same direction as
the force vector.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's Three Laws does the
following statement satisfy? For every action
there is an equal and opposite reaction.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's Three Laws does the
following statement satisfy?
Every object in a state of uniform motion tends
to remain in that state of motion unless an
external force is applied to it.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's three laws does the
following example illustrate?
If you have a hockey puck sliding along a table,
it will eventually come to a stop.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which law states the need to wear seatbelts?
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: none of the above
Which of Newton's Three Laws does the
following statement satisfy?
The relationship between an object's mass (m),
its acceleration (a), and the applied force F is
F=ma. Acceleration and force are vectors. This
law requires that the direction of the
acceleration vector is in the same direction as
the force vector.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's Three Laws does the
following statement satisfy? For every action
there is an equal and opposite reaction.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's Three Laws does the
following statement satisfy?
Every object in a state of uniform motion tends
to remain in that state of motion unless an
external force is applied to it.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which of Newton's three laws does the
following example illustrate?
If you have a hockey puck sliding along a table,
it will eventually come to a stop.
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: All of the above
Which law states the need to wear seatbelts?
A: Newton's First Law
B: Newton's Second Law
C: Newton's Third Law
D: none of the above
Section 4.4: Everyday Forces
Holt Physics
Chapter 4 Section 4
Pages 133-141
Everyday Forces
• Weight – the magnitude of the force
of gravity acting on an object
Everyday Forces
Fg = mg
Fg = force due to gravity (in Newtons)
m = mass of object (in kilograms)
g = acceleration due to gravity (-9.81 m/s2)
* Mass ≠ Weight
Everyday Forces
• Normal Force – (Fn) – a contact force
exerted by one object on another in
a direction perpendicular to the
surface of contact. On a horizontal
surface, Fn = mg
Everyday Forces
• Normal force diagrams-
Everyday Forces
• Frictional Forces – Contact forces which
oppose applied forces
• These are the surfaces in contact at a
microscopic level.
Everyday Forces
Static friction - (Fs) - force exerted
on a motionless object by the
environment to
resist an
external force
attempting to
cause a change
in motion
Everyday Forces
Kinetic friction – (Fk) – force
exerted on a moving object that
opposes
motion
• * Fk < Fs due to surface adhesion
between two surfaces in contact
• Coefficient of friction (μ) – a ratio of
frictional force to normal force
between two objects
Coefficient of Friction
The coefficient of friction is a ratio of force of
friction to the normal force acting between two
objects.
-This completely depends on the objects in
contact.
-Different experimental values have been
calculated based on the materials in contact
(page 136: table 4-7)
Coefficient of Friction Equations
• Coefficient of static friction
μs =
Fs,max
Fn
• Coefficient of kinetic friction
μk =
Fk
Fn
Sample problem
• Page 145 #35
95Kg clock initially at rest on a horizontal floor
requires 650N force to set it in motion.
After the clock is in motion, a force of 560N
keeps it moving with a constant velocity.
Find the coefficient of static and kinetic friction
between the clock and the floor.
Everyday Forces
Air resistance is
a form of friction
 as velocity
increases so does
air resistance
The four fundamental forces of Physics
https://www.youtube.com/watch?v=a6skWBuHaE