N e w t o n s L a w s Unit 3 Slide 2 3.1 Force and Mass Slide 3
3.1 Force and mass Force push or pull; required to change an
objects motion. Vector so magnitude and direction Example of
Contact Forces Friction Tension Applied Spring Examples of Field
Forces Gravitational Electric Magnetic Slide 4 3.1 Force and mass
Mass measurement of how difficult it is to change the objects
velocity Inertia resistance to change in velocity So mass is a
measurement of an objects inertia Slide 5 3.2 Newtons First Law of
Motion Slide 6 1 st Law An object at rest remains at rest as long
as no net force acts on it. An object moving with constant velocity
continues to move with the same speed and in the same direction as
long as no net force acts on it. Slide 7 3.2 Newtons First Law of
Motion Sometimes called the Law of Inertia Slide 8 3.3 Newtons
Second Law of Motion Slide 9 2 nd Law A net force causes an
acceleration in the direction of the net force. Simulation Slide 10
3.3 Newtons Second Law of Motion Free body diagrams Show all the
forces acting on an object For example an object sitting on a table
W weight = mg N Normal Force (perpendicular) to the surface N W
Slide 11 3.3 Newtons Second Law of Motion Free body diagrams If a
rope pulls the object toward the right, then T = Tension N W T
Practice Free Body Slide 12 3.3 Newtons Second Law of Motion Free
body diagrams Steps in problems solving 1.Sketch the forces
2.Isolate the Object 3.Choose a Coordinate System 4.Resolve the
Forces into Components 5.Apply Newtons Second Law of Motion Slide
13 3.3 Newtons Second Law of Motion A 50 kg gopher has a string
tied around his neck and pulled with a force of 80 N at an angle of
30 o to the horizontal. What is his acceleration? Slide 14 3.3
Newtons Second Law of Motion A 50 kg gopher has a string tied
around his neck and pulled with a force of 80 N at an angle of 30 o
to the horizontal. What is his acceleration? Free Body diagram
Slide 15 3.3 Newtons Second Law of Motion A 50 kg gopher has a
string tied around his neck and pulled with a force of 80 N at an
angle of 30 o to the horizontal. What is his acceleration? Free
Body diagram N W T Slide 16 3.3 Newtons Second Law of Motion A 50
kg gopher has a string tied around his neck and pulled with a force
of 80 N at an angle of 30 o to the horizontal. What is his
acceleration? Free Body diagram Axis N W T Slide 17 3.3 Newtons
Second Law of Motion A 50 kg gopher has a string tied around his
neck and pulled with a force of 80 N at an angle of 30 o to the
horizontal. What is his acceleration? Free Body diagram Axis N W T
TyTy TxTx Slide 18 3.3 Newtons Second Law of Motion A 50 kg gopher
has a string tied around his neck and pulled with a force of 80 N
at an angle of 30 o to the horizontal. What is his acceleration?
Free Body diagram Axis Equation N W TyTy TxTx Slide 19 3.4 Newtons
Third Law of Motion Slide 20 For every force that acts on an
object, there is a reaction force acting on a different object that
is equal in magnitude and opposite in direction. If object 1 exerts
a force F on object 2, then object 2 exerts a force F on object 1.
Slide 21 3.4 Newtons Third Law of Motion What are the action
reaction pairs in the following? Slide 22 3.4 Newtons Third Law of
Motion A 60 kg man walks off a 3 m long canoe by walking from one
end to the other. He applies a force of 20 N to the canoe, which
has a mass of 150 kg. A.What is the acceleration of the man? B.
What is the acceleration of the canoe? Slide 23 3.4 Newtons Third
Law of Motion A 60 kg man walks off a 3 m long canoe by walking
from one end to the other. He applies a force of 20 N to the canoe,
which has a mass of 150 kg. Free Body Diagrams P NcNc WcWc P WmWm
NmNm Slide 24 3.4 Newtons Third Law of Motion A 60 kg man walks off
a 3 m long canoe by walking from one end to the other. He applies a
force of 20 N to the canoe, which has a mass of 150 kg. Equations P
NcNc WcWc P WmWm NmNm Slide 25 3.4 Newtons Third Law of Motion A 60
kg man walks off a 3 m long canoe by walking from one end to the
other. He applies a force of 20 N to the canoe, which has a mass of
150 kg. A-acceleration of man P NcNc WcWc P WmWm NmNm Slide 26 3.4
Newtons Third Law of Motion A 60 kg man walks off a 3 m long canoe
by walking from one end to the other. He applies a force of 20 N to
the canoe, which has a mass of 150 kg. A acceleration of canoe P
NcNc WcWc P WmWm NmNm Slide 27 3.4 Newtons Third Law of Motion Two
boxes are tied together with a rope, and the first one is pulled by
a second rope. Both boxes accelerate at 2.0 m/s 2. If the front box
has a mass of 25 kg, and the second a mass of 50 kg, what is the
tension on each rope? a Slide 28 3.4 Newtons Third Law of Motion
Free body diagrams NfNf WfWf T1T1 T2T2 WbWb NbNb T2T2 Slide 29 3.4
Newtons Third Law of Motion Equations Solve (add) NfNf WfWf T1T1
T2T2 WbWb NbNb T2T2 Slide 30 3.5 The Vector Nature of Forces Slide
31 Forces are vectors, so they can be treated using vectors rules
Slide 32 3.5 The Vector Nature of Forces Two men are carrying a 1.3
kg pail of water, the first dude (Bob) exerts a force of 7N, and
the second one (Leon) exerts a force of 11N @ 28 o. What is the
angle of Bobs force? Free Body Diagram? W L B Slide 33 3.5 The
Vector Nature of Forces Two men are carrying a 1.3 kg pail of
water, the first dude (Bob) exerts a force of 7N, and the second
one (Leon) exerts a force of 11N @ 28 o. What is the angle of Bobs
force? Components? W L BByBy BxBx Slide 34 3.5 The Vector Nature of
Forces Two men are carrying a 1.3 kg pail of water, the first dude
(Bob) exerts a force of 7N, and the second one (Leon) exerts a
force of 11N @ 28 o. What is the angle of Bobs force? Components? W
L ByBy BxBx LyLy LxLx Slide 35 3.5 The Vector Nature of Forces Two
men are carrying a 1.3 kg pail of water, the first dude (Bob)
exerts a force of 7N, and the second one (Leon) exerts a force of
11N @ 28 o. What is the angle of Bobs force? Equations? W ByBy BxBx
LyLy LxLx Slide 36 3.5 The Vector Nature of Forces Two men are
carrying a 1.3 kg pail of water, the first dude (Bob) exerts a
force of 7N, and the second one (Leon) exerts a force of 11N @ 28
o. What is the angle of Bobs force? Values? W ByBy BxBx LyLy LxLx
Slide 37 3.5 The Vector Nature of Forces Two men are carrying a 1.3
kg pail of water, the first dude (Bob) exerts a force of 7N, and
the second one (Leon) exerts a force of 11N @ 28 o. What is the
angle of Bobs force? Values? W ByBy BxBx LyLy LxLx Slide 38 3.5 The
Vector Nature of Forces Two men are carrying a 1.3 kg pail of
water, the first dude (Bob) exerts a force of 7N, and the second
one (Leon) exerts a force of 11N @ 28 o. What is the angle of Bobs
force? Solve? W ByBy BxBx LyLy LxLx Slide 39 3.5 The Vector Nature
of Forces Two men are carrying a 1.3 kg pail of water, the first
dude (Bob) exerts a force of 12.3N, and the second one (Leon)
exerts a force of 11N @ 28 o. What is the angle of Bobs force?
Solve? W ByBy BxBx LyLy LxLx Slide 40 3.6 Frictional Forces Slide
41 Friction force that opposes motion Caused by microscopic
irregularities of a surface Increases as pushing force increases
Slide 42 3.6 Frictional Forces Depends on the normal force and the
type of surface f force of friction (N) N normal force coefficient
of friction (1 or less) Slide 43 3.6 Frictional Forces Three types
of friction 1.Static object at rest 2.Kinetic object in motion
3.Rolling just like it sounds Surfaces (static) (kinetic) Steel on
steel0.740.57 Glass on glass0.940.4 Metal on Metal
(lubricated)0.150.06 Ice on ice0.10.03 Teflon on Teflon0.04 Tire on
concrete10.8 Tire on wet road0.60.4 Tire on snow0.30.2 Slide 44 3.6
Frictional Forces Example
