Physics Department
PHYS 1P21/1P91
Outline
Textbook
Homework
Introduction
Kinematics
Dynamics
Rotational Motion
Work, energy and Momentum
Oscillations and Waves
Formula Sheet
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1P21_Crandles
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Dynamics
Mechanics and Waves
Introduction
Kinematics: motion in one and two dimensions
Dynamics
Newton's First and Second Laws
The "natural" state of an object:
Aristotle
vs.
Galileo
Frames of
Reference
Newton's
First Law
MC:
force from motion I
MC:
force from motion II
MC:
force from motion III
MC:
force from motion IV
Definition:
mass and inertia
Table Cloth Trick
MC:
which direction does the collision occur?
MC:
which part of the brain would injured?
Net Force and Newton's
Second Law
MC:
net force and acceleration
Ex:
two horizontal forces
Ex:
ranking net force and acceleration
Ex:
a skydiver
Ex:
compare the masses
Ex:
independence of components
Ex:
a ship
Inertial reference frames
Reference
Frames
Definition of
inertial reference frame
Inertial Reference
Frames
Non-Inertial Reference Frames and
fictitious
forces
Fictitious Forces:
e.g.Coriolus Force
Ex:
which are inertial frames of reference?
the laws of physics are independent of
reference frame
Types of Forces
Non-contact forces: gravitational force
Universal law of
gravitation
Universal law and
acceleration due to gravity
acceleration due to gravity on different
planets
Constant acceleration
near the surface
mass
(inertia - scalar ) is
NOT weight
(force of gravity - vector)
Contact forces
Normal Force: molecular
"spring mattress"
is the origin of normal force
Frictional Force: molecular
"cold welds"
is the origin of friction
Tension: massless rope is a perfect transmitter of force:
straight
or
wrapped around an ideal pulley
Free Body Diagrams
free body diagram
elevator accelerating upward
free body diagram
of a rocket propelled ice block
free body diagram
of a skier being towed up a hill
MC:
Which is the correct FBD ?
MC:
lowering a crate
MC:
motion in an elevator I
MC:
motion in an elevator II
Ex:
In which rope is tension larger?
Ex:
rappelling down a cliff
Newton's
Third Law
MC:
identify action-reaction pair I
MC:
identify action-reaction pair II
MC:
a collision
MC:
father and daughter on skates
MC:
tug of war
MC:
motion in an elevator III
Coupled Objects
Two blocks on frictionless surface
MC:
two coupled hanging objects
Ex:
motion with a pulley I
MC:
motion with a pulley II
Frictional Force
molecular
"cold welds"
is the origin of friction
Static Friction
implies no slipping;
balances applied force
Static Friction has
variable magnitude
Kinetic Friction
occurs when an object is sliding;
is opposite to motion
static
friction
balances applied force
; kinetic friction opposite to velocity
kinetic
friction
opposes motion
Kinetic Friction has
has approximately constant value
MC:
pushing a box on rough surface
MC:
pushing a heavy crate
MC:
box on the bed of a truck
MC:
static
vs.
kinetic friction
Ex:
accelerating on ice
Ex:
static
vs.
kinetic friction
MC:
pulling a block 1
MC:
pulling a block 2
MC:
pulling a block 3
MC:
block against wall
Ex:
pushing two blocks
Drag and terminal velocity
Drag force depends on velocity:
low speed
Drag force depends on velocity:
greater speed
Drag force depends on velocity:
terminal velocity
MC:
ball thrown down with speed 30 m/s, terminal velocity is 15 m/s
MC:
opening a parachute
Linearly Constrained Motion
Ex:
Determine the
critical angle
Ex:
Truck on a steep road
Ex:
friction on an inclined plane: will it slide back down?
Ex:
Coupled objects on an inclined plane
MC:
increasing weight on an inclined plane
Uniform Circular Motion
Centripetal Acceleration
uniform circular motion
defined
angular position, frequency period
angular
velocity
and tangential velocity
Every particle in rigid body shares same ω but
tangential velocity
depends on radius
Direction of
centripetal acceleration
MC:
centripetal acceleration I
MC:
centripetal acceleration II
MC:
centripetal acceleration III
Ex:
tight and gentle turns
the kinematic equations do NOT apply to uniform circular motion
non-uniform circular motion:
a
=
a
t
+
a
c
(
a model plane
,
a discus thrower
)
N2L: Net Force must provide centripetal acceleration
a model airplane,
F
c
= T
provided by tension in the wire
a turning car,
F
c
= f
s
provided by friction
a banked road,
F
c
provided by the normal force
A carnival ride,
F
c
provided by the tension force
MC:
dip in the road
MC:
hill on the road
MC:
ferris wheel
MC:
ball moving on a string in a vertical circle
Gravitational Force and Kepler's Laws
MC:
gravitational force I
MC:
gravitational force II
MC:
gravitational force III
MC:
gravitational force IV
Ex:
three objects in a line in outer space
Big "G" vs. little "g"
perspectives
MC:
Weight and gravitational force
Terrestrial versus celestial dynamics
An old distinction:
Celestial
Physics
vs. terrestrial physics
solar system
planetary orbit eccentricity
planetary data
Kepler's laws
Weightlessness in the
international space station
Terrestrial
and
Celestial
Dynamics are the same
In orbit, an object is continuously
falling
an orbiting satellite,
F
c
provided by gravity
Rotational motion
Work, energy, momentum
Oscillations and waves
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