The Simple Pendulum
Consider a mass m attached to a
string of length L which is free to
swing back and forth.
If it is displaced from its lowest
position by an angle , Newtons
second law for the tangential
component of gravity, parallel
to the motion, i
Explain the pendulum in terms of energy.
Answer
Work!
We were considering the
car as our system, however,
energy was being
transferred from the car to
the track via friction.
W > 0: The environment does work on the system and
the systems energy increase
Consider the following two situations:
Situation I: A car on Earth rides over the top of a round hill, with radius of
curvature = 100 m, at constant speed v = 35 mph.
Situation II: A monorail car in intergalactic space (no gravity) moves along a
round mon
The Rigid-Body Model
A rigid body is an
extended object whose
size and shape do not
change as it moves.
No real object is perfectly
rigid, but we will
approximate rotating
objects as perfectly rigid.
This simplification is the
rigid-body model.
Rotational
1st Exam! Friday the 10th!
1 formula sheet SINGLE SIDED, No worked out examples, Handed in
with exam
Calculator
Writing utensil(s)
Do NOT forget, I will not bring extras!
Format (see cc for example of previous exam)
1/3rd multiple choice
2/3rd quantita
Exam in 1 week
Homework assignments posted. Ch 7 and 8 due on exam day
(midnight)
Consider the situation shown below. m1 is 7.0 kg, m2 is 20.0 kg. Both boxes have a
coefficient of kinetic friction of = 0.18. What is the Tension in the rope connecting the
QuickCheck 5.13
A ball, hanging from the ceiling by a
string, is pulled back and released. Which
is the correct free-body diagram just after
its release?
A.
B.
C.
D.
E.
QuickCheck 5.13
A ball, hanging from the ceiling by a
string, is pulled back and relea
Demo: Look at how forces relate to motion
frictionless track,
Fan applies a constant force
How does cart move?
Demo: Look at how forces relate to motion
frictionless track,
Fan applies a constant force
How does cart move?
What if the cart gets heav
QuickCheck 14.1
Which oscillation (or oscillations) is SHM?
D. A and B but not C.
E. None are.
QuickCheck 14.1
Which oscillation (or oscillations) is SHM?
D. A and B but not C.
E. None are.
Simple Harmonic Motion and Circular Motion
Figure (a) shows a sh
Chapter 5 Preview
What Is a Force?
A force is a push or a pull.
A force acts on an object.
Pushes and pulls are applied to
something.
From the objects perspective, it
has a force exerted on it.
What Is a Force?
A force requires an agent,
something th
Extra credit anyone?
For 1% added to your final grade
enter a car into the rocket car races
on April 18th
write a brief (1 page) summary
describing design and decisions
related to design
can be a group project if
no more than 5 ppl in group
all 5 peo
Oscillations and simple harmonic motion
What is an oscillation?
Oscillatory Motion
Objects that undergo a repetitive
motion back and forth around an
equilibrium position are called
oscillators.
The time to complete one full cycle, or
one oscillation, is
Up until now weve been talking about small singular disturbances to
the medium
This produces a single pulse
What happens if we have a regular continuous disturbance, from, for
example, a harmonic oscillator?
Sinusoidal Waves
A wave source at x = 0 that
Exam Results
Energy
Energy in an isolated system is conserved (can change forms)
Weve learned about 3 forms Ug=mgh; Usp,=1/2k(s)2;K=1/2mv2
Thinking about situations like this amounts to bookkeeping, keeping
track of where that energy is
, = ,
, + , + =
Sinusoidal Waves
The distance spanned by one cycle of the motion is
called the wavelength of the wave. Wavelength
is measured in units of meters.
During a time interval of exactly one period T, each
crest of a sinusoidal wave travels forward a
distance
The Principle of Superposition
The figure shows the
superposition of two waves
on a string as they pass
through each other.
The principle of
superposition comes into
play wherever the waves
overlap.
The solid line is the sum at
each point of the two
di
Work and Kinetic Energy
Consider a force acting on a
particle which moves along
the s-axis.
The force component Fs
causes the particle to speed up
or slow down, transferring
energy to or from the particle.
The force does work on the particle:
The unit
QuickCheck 10.7
Three balls are thrown from a
cliff with the same speed but at
different angles. Which ball has
the greatest speed just before it
hits the ground?
A.
Ball A.
B.
Ball B.
C.
Ball C.
D.
All balls have the same speed.
E.
Not enough information
Example 20.8 Light Traveling Through Glass
nglass = 1.5
The Doppler Effect
A source of sound waves moving away from Pablo
and toward Nancy at a steady speed vs.
After a wave crest leaves the source, its motion is
governed by the properties of the medium
Consequences of Moment of Inertia
Easier to spin up
Harder to spin up
Calculating the Moment of Inertia
The Parallel-Axis Theorem
You do sometimes need to know the moment of inertia
about an axis in an unusual position.
You can find it if you know the m
The Vector Description of Rotational Motion
One-dimensional motion uses a scalar velocity v
and force F.
A more general understanding of motion
requires vectors and .
Similarly, a more general description of rotational
motion requires us to replace the
Imagine an firecracker floating in space (ie. ignore gravity)
Imagine an firecracker floating in space (ie. ignore gravity)
Now imagine it exploding
Imagine an firecracker floating in space (ie. ignore gravity)
Now imagine it exploding
Question: Did it mo
Fictitious Forces
If you are riding in a car that
makes a sudden stop, you
seem to be hurled forward.
You can describe your
experience in terms of
fictitious forces.
Fictitious forces are not real
because no agent is exerting
them.
Fictitious forces d
QuickCheck 4.2
A car is traveling around a curve at
a steady 45 mph. Is the car
accelerating?
A.
Yes
B.
No
QuickCheck 4.2
A car is traveling around a curve at
a steady 45 mph. Is the car
accelerating?
A. Yes
B.
No
QuickCheck 4.1
A particle undergoes accel
Time to be quantitative
On Planet X, a rock is thrown straight up. The position of the ball at various times is
listed below. (Note: I chose "up" as the "+" direction)
What is the velocity of the ball on
Planet X?
Time(s)
Height
(m)
0
0
1
17.5
2
30
3
37.5
Non-uniform motion
100
75
X (m)
50
25
0
0
1
2
t (seconds)
3
4
Instantaneous Velocity
A Little Calculus: Derivatives
ds/dt is called the derivative of s with respect to t.
ds/dt is the slope of the line that is tangent to the positionversus-time graph.
Physics 201:
Mechanics and Sound
Prof. Justin Perron
[email protected]
Office: 229 Science 2
Phone: (760) 750 - 8501
Office hours: Thursday 9:00 11:00 am
Or by appointment
Physics
Everything happens for a reason.and that reason
is usually Physics
- Some m
Recap
1)
Description of motion (motion diagrams, graphs, pictures)
i.
ii.
iii.
Position
Velocity
Acceleration
All with respect to time
2)
Visual and graphical representations
3)
Average values Calculus
4)
Kinematic equations for constant acceleration
Vect
Homework 1
Due Friday
Log on early to deal with any MP issues
Describing motion
Position: where is it?
Velocity: how is position changing in time?
Acceleration: how is velocity changing in time?
A race car (shown as a dot) is moving as shown in the (one
PHYS 201 Exam 2
Name:
March 14, 2016.
Lab day: Wed or Fri
Time allotted for the examination is the full 50 minute period.
Students are allowed the following:
Calculator
1 formula sheet with NO WORKED OUT PROBLEMS!
These are to be submitted with your exa
Calculating the Moment of Inertia
Torque
The effectiveness of a force at causing a rotation is called
torque. Torque is the rotational equivalent of force.
Constraints Due to Ropes and Pulleys
A rope passes over a pulley
and is connected to an
object in
Up to now
Chapters 1-2: Describing motion and 1D kinematics (position,
velocity, acceleration)
Chapters 2-4: Vectors and motion in 2 dimensions and circular motion
Chapter 5-9: Forces & Newtons laws, =
Chapter 10: Momentum, no external forces conserv
Example 21.10 Two-Dimensional Interference
Between Two Loudspeakers
Example 21.10 Two-Dimensional Interference
Between Two Loudspeakers
Example 21.10 Two-Dimensional Interference
Between Two Loudspeakers
Example 21.10 Two-Dimensional Interference
Between
8) Ash is trying to catch the best pokemon ever Jigglypuff. Ash throws his pokeball horizontally
1.75 m above the ground. How fast must he throw the ball if he wants it to land at J igglypuff 5
feet 14.2 m away? (assume the ground is at)
+Lq At: XAwadko
Exam Results
Average = 25/42 (60%)
St. dev = 10.1 (23%)
If you are not doing as well you want, ask
Am I
Reading before class?
Doing all HW and revisions?
Coming to class and actively
participating?
Attending lab and actively
participating?
Trying to unde