Read: Chap 4 09/16/14 – slide 1
A100–Exploring the Universe: The Laws of Motion
Martin D. Weinberg
UMass Astronomy
September 16, 2014
Announcements
⊲ Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 2
MasteringAstronomy pointers (see Handouts) [example]
Announcements
⊲ Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 2
MasteringAstronomy pointers (see Handouts) [example]
Astronomy Help Desk
⊲ Mon through Thu, 7-9pm in Hasbrouck 110
Announcements
⊲ Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 2
MasteringAstronomy pointers (see Handouts) [example]
Astronomy Help Desk
⊲ Mon through Thu, 7-9pm in Hasbrouck 110
Today’s topic: Newton’s Laws of Motion and Gravity
⊲ How do we describe motion?
⊲ How is mass different from weight?
⊲ How did Newton change our view of the Universe?
⊲ What are Newton’s 3 Laws of Motion?
Announcements
⊲ Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 2
MasteringAstronomy pointers (see Handouts) [example]
Astronomy Help Desk
⊲ Mon through Thu, 7-9pm in Hasbrouck 110
Today’s topic: Newton’s Laws of Motion and Gravity
⊲ How do we describe motion?
⊲ How is mass different from weight?
⊲ How did Newton change our view of the Universe?
⊲ What are Newton’s 3 Laws of Motion?
Questions?
Scientific Progress
Read: Chap 4 09/16/14 – slide 3
“If I have seen farther than others, it is
because I have stood on the shoulders
of giants”
—Isaac Newton
Back to Galileo (review)
Announcements
Scientific Progress
⊲ Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 4
Similarity of Earth–Moon–Sun andJupiter–moons–Sun
Rolled balls down inclined planes
Found that objects increased their speed independently
of weight
Uniform, straight-line motion is the natural state for
motion of objects
Galilean relativity
⊲ The mechanical laws of physics are the same for
every inertial observer.
⊲ By observing the outcome of mechanical
experiments, one cannot distinguish a state of rest
from a state of constant velocity.
Back to Galileo (review)
Announcements
Scientific Progress
⊲ Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 4
Similarity of Earth–Moon–Sun andJupiter–moons–Sun
Rolled balls down inclined planes
Found that objects increased their speed independently
of weight
Uniform, straight-line motion is the natural state for
motion of objects
Galilean relativity
⊲ The mechanical laws of physics are the same for
every inertial observer.
⊲ By observing the outcome of mechanical
experiments, one cannot distinguish a state of rest
from a state of constant velocity.
Back to Galileo (review)
Announcements
Scientific Progress
⊲ Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 4
Similarity of Earth–Moon–Sun andJupiter–moons–Sun
Rolled balls down inclined planes
Found that objects increased their speed independently
of weight
Uniform, straight-line motion is the natural state for
motion of objects
Galilean relativity
⊲ The mechanical laws of physics are the same for
every inertial observer.
⊲ By observing the outcome of mechanical
experiments, one cannot distinguish a state of rest
from a state of constant velocity.
Back to Galileo (review)
Announcements
Scientific Progress
⊲ Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 4
Similarity of Earth–Moon–Sun andJupiter–moons–Sun
Rolled balls down inclined planes
Found that objects increased their speed independently
of weight
Uniform, straight-line motion is the natural state for
motion of objects
Galilean relativity
⊲ The mechanical laws of physics are the same for
every inertial observer.
⊲ By observing the outcome of mechanical
experiments, one cannot distinguish a state of rest
from a state of constant velocity.
Back to Galileo (review)
Announcements
Scientific Progress
⊲ Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 5
Example: centripetal motion
State of motion called inertia
Objects preserve their inertia unless acted on by a force
Acceleration by Gravity
Read: Chap 4 09/16/14 – slide 6
All falling objects accelerate at
the same rate (not counting fric-
tion of air resistance)
On Earth, g ≈ 10m/s2: speed
increases 10m/s with each sec-
ond of falling
Note: ≈ means approximately equal
Acceleration by Gravity
Announcements
Scientific Progress
Galileo
⊲Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 7
Galileo showed that g is
the same for all falling
objects, regardless of their
mass.
Acceleration by Gravity
Announcements
Scientific Progress
Galileo
⊲Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 8
Galileo’s thought experiment
Earth is sphere
Shoot a cannonball fast
enough and rate of falling
will balance curvature
[demos]
Describing motion
Read: Chap 4 09/16/14 – slide 9
Precise definitions to describe motion:
Speed: Rate at which object moves
speed =distance
time
[units of m/s, cm/s, km/s or miles/hr,
example: 10 m/s]
Velocity: Speed plus direction example:
10 m/s due East
Acceleration: Any change in velocity in
units of speed/time (m/s2) and a direc-
tion
Momentum and Force
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
⊲Momentum &Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 10
Momentum = mass × velocity
A net force changes momentum, which generally means
an acceleration (change in velocity)
Rotational momentum of a spinning or orbiting object is
known as angular momentum
Rotational force is known as torque
[demo]
Momentum and Force
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
⊲Momentum &Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 10
Momentum = mass × velocity
A net force changes momentum, which generally means
an acceleration (change in velocity)
Rotational momentum of a spinning or orbiting object is
known as angular momentum
Rotational force is known as torque
[demo]
Momentum and Force
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
⊲Momentum &Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 10
Momentum = mass × velocity
A net force changes momentum, which generally means
an acceleration (change in velocity)
Rotational momentum of a spinning or orbiting object is
known as angular momentum
Rotational force is known as torque
[demo]
Momentum and Force
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
⊲Momentum &Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 10
Momentum = mass × velocity
A net force changes momentum, which generally means
an acceleration (change in velocity)
Rotational momentum of a spinning or orbiting object is
known as angular momentum
Rotational force is known as torque
[demo]
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop.
2. A bus speeding up.
3. An elevator moving up at constant speed.
4. A bicycle going around a curve.
5. A moon orbiting Jupiter.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop. Y
2. A bus speeding up.
3. An elevator moving up at constant speed.
4. A bicycle going around a curve.
5. A moon orbiting Jupiter.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop. Y
2. A bus speeding up. Y
3. An elevator moving up at constant speed.
4. A bicycle going around a curve.
5. A moon orbiting Jupiter.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop. Y
2. A bus speeding up. Y
3. An elevator moving up at constant speed. N
4. A bicycle going around a curve.
5. A moon orbiting Jupiter.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop. Y
2. A bus speeding up. Y
3. An elevator moving up at constant speed. N
4. A bicycle going around a curve. Y
5. A moon orbiting Jupiter.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
⊲ Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 11
Is there a net force? Y/N
1. A car coming to a stop. Y
2. A bus speeding up. Y
3. An elevator moving up at constant speed. N
4. A bicycle going around a curve. Y
5. A moon orbiting Jupiter. Y
Mass and weight
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
⊲ Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 12
How is mass different from weight?
Mass—the amount of matter in an object
Weight—the force that acts upon an object
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
⊲ Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 13
On the Moon:
1. My weight is the same, my mass is less.
2. My weight is less, my mass is the same.
3. My weight is more, my mass is the same.
4. My weight is more, my mass is less.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
⊲ Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 13
On the Moon:
1. My weight is the same, my mass is less.
2. My weight is less, my mass is the same.
3. My weight is more, my mass is the same.
4. My weight is more, my mass is less.
Weightlessness
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
⊲ Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 14
Why are astronauts weightless in space?
There is gravity in
space
Weightlessness is
due to a constant
state of free-fall
Newton
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
⊲ Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 15
Newton’s significant contributions
Recognized importance of
Galileo’s contribution
Laws of Motion
Law of Gravitation
Newton
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
⊲ Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 15
Newton’s significant contributions
Recognized importance of
Galileo’s contribution
Laws of Motion
Law of Gravitation
Invented differential calculus
Newton
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
⊲ Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 16
Newton changed our view of the universe!
Realized the same physical laws
that operate on Earth also oper-
ate in the heavens
One Universe
Discovered laws of motion and
gravity
Much more: Experiments with
light; first reflecting telescope,
calculus. . .
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 17
1. Law of Inertia: A body remains at rest, or moves in a
straight line at a constant speed, unless acted on by an
outside force
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 17
1. Law of Inertia: A body remains at rest, or moves in a
straight line at a constant speed, unless acted on by an
outside force
2. Second Law: Acceleration of an object is proportional to
the force acting on that object
F = m a
m is mass
a is acceleration
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 17
1. Law of Inertia: A body remains at rest, or moves in a
straight line at a constant speed, unless acted on by an
outside force
2. Second Law: Acceleration of an object is proportional to
the force acting on that object
F = m a
m is mass
a is acceleration
3. Third Law: When one body exerts a force on a second
body, the second body exerts an equal and opposite force on
the first body
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 18
First Law: Law of Inertia
The motion of an object has speed and direction known
as momentum
An object’s resistance to changes in motion is known as
inertia
Contradicted the still popular theories of Aristotle that
objects will eventually come to rest
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 19
Second Law of Motion
F= ma
⊲ F describes the force acting
⊲ m is the mass of the object
⊲ a is its acceleration, the change in its motion.
Like motion, force has both a value or strength, and a
direction in which it acts.
Acceleration refers to any change (e.g. both “speeding
up” or “slowing down”)
Implies First Law of Motion
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 20
Second Law of Motion: examples
The larger the force ⇒ the larger the acceleration
For equal force, a larger mass must have a smaller
acceleration
Larger mass has greater inertia. Can use this to measure
mass of an object
Unit of force (metric) is called a Newton (N):
1 Newton is equal to 1 kg · m/s2
Inertial mass
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 21
Third Law: equal and opposite force
Example: smack an object
⊲ Object moves as a result
⊲ Your hand also feels a force and bounces backn
(and hurts)
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 21
Third Law: equal and opposite force
Example: smack an object
⊲ Object moves as a result
⊲ Your hand also feels a force and bounces backn
(and hurts)
Example: small object hits a large object
⊲ If the forces are equal, why does the smaller object
bounce back faster?
Newton’s 3 Laws of Motion
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
⊲ 3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 21
Third Law: equal and opposite force
Example: smack an object
⊲ Object moves as a result
⊲ Your hand also feels a force and bounces backn
(and hurts)
Example: small object hits a large object
⊲ If the forces are equal, why does the smaller object
bounce back faster?
⊲ msmallasmall = F = mlargealarge
⊲ asmall =mlarge
msmallalarge
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
⊲ Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 22
Is the force the Earth exerts on you larger, smaller, or the same
force you exert on it?
Earth exerts a larger force on you.
You exert a larger force on Earth.
You and the Earth exert equal and opposite forces on
each other.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
⊲ Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 22
Is the force the Earth exerts on you larger, smaller, or the same
force you exert on it?
Earth exerts a larger force on you.
You exert a larger force on Earth.
You and the Earth exert equal and opposite forces on
each other.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
⊲ Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 22
Is the force the Earth exerts on you larger, smaller, or the same
force you exert on it?
Earth exerts a larger force on you.
You exert a larger force on Earth.
You and the Earth exert equal and opposite forces on
each other.
⊲ msmallasmall = F = mlargealarge
⊲ alarge =msmall
mlargeasmall
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
⊲ Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 23
A compact car and a Mack truck have a head-on collision. Are
the following true or false?
1. The force of the car on the truck is equal and opposite to
the force of the truck on the car.
2. The momentum transferred from the truck to the car is
equal and opposite to the momentum transferred from
the car to the truck.
3. The change of velocity of the car is the same as the
change of velocity of the truck.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
⊲ Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 23
A compact car and a Mack truck have a head-on collision. Are
the following true or false?
1. The force of the car on the truck is equal and opposite to
the force of the truck on the car. T
2. The momentum transferred from the truck to the car is
equal and opposite to the momentum transferred from
the car to the truck.
3. The change of velocity of the car is the same as the
change of velocity of the truck.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
⊲ Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 23
A compact car and a Mack truck have a head-on collision. Are
the following true or false?
1. The force of the car on the truck is equal and opposite to
the force of the truck on the car. T
2. The momentum transferred from the truck to the car is
equal and opposite to the momentum transferred from
the car to the truck. T
3. The change of velocity of the car is the same as the
change of velocity of the truck.
Thought question
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
⊲ Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 23
A compact car and a Mack truck have a head-on collision. Are
the following true or false?
1. The force of the car on the truck is equal and opposite to
the force of the truck on the car. T
2. The momentum transferred from the truck to the car is
equal and opposite to the momentum transferred from
the car to the truck. T
3. The change of velocity of the car is the same as the
change of velocity of the truck. F
Conservation Laws
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
⊲ConservationLaws
Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 24
Why do objects move at constant velocity if no force acts
on them?
What keeps a planet rotating and orbiting the Sun?
Where do objects get their energy?
Conservation of Momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
⊲Conservation ofMomentum
Angular Momentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 25
The total momentum of
interacting objects cannot
change unless an external
force is acting on them
Interacting objects ex-
change momentum
through equal and oppo-
site forces
Angular Momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
⊲AngularMomentum
Conservation ofAngular momentum
Read: Chap 4 09/16/14 – slide 26
What keeps a planet rotating and orbiting theSun?
Conservation of Angular momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
⊲
Conservation ofAngularmomentum
Read: Chap 4 09/16/14 – slide 27
angular momentum = mass × velocity × radius
The angular momentum of an object cannot change
unless an external twisting force (torque) is acting on it
Earth experiences no twisting force as it orbits the Sun,
so its rotation and orbit will continue indefinitely
Bicycle wheel with perfect bearings will turn indefinitely
Conservation of Angular momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
⊲
Conservation ofAngularmomentum
Read: Chap 4 09/16/14 – slide 27
angular momentum = mass × velocity × radius
The angular momentum of an object cannot change
unless an external twisting force (torque) is acting on it
Earth experiences no twisting force as it orbits the Sun,
so its rotation and orbit will continue indefinitely
Bicycle wheel with perfect bearings will turn indefinitely
Conservation of Angular momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
⊲
Conservation ofAngularmomentum
Read: Chap 4 09/16/14 – slide 27
angular momentum = mass × velocity × radius
The angular momentum of an object cannot change
unless an external twisting force (torque) is acting on it
Earth experiences no twisting force as it orbits the Sun,
so its rotation and orbit will continue indefinitely
Bicycle wheel with perfect bearings will turn indefinitely
Conservation of angular momentum
Announcements
Scientific Progress
Galileo
Acceleration byGravity
Describing motion
Momentum & Force
Thought question
Mass and weight
Thought question
Weightlessness
Newton
3 Laws of Motion
Thought question
Thought question
Conservation Laws
Conservation ofMomentum
Angular Momentum
⊲
Conservation ofAngularmomentum
Read: Chap 4 09/16/14 – slide 28
Angular momentum conservation also explains why objects
rotate faster as they shrink in radius:
Tutorials
Read: Chap 4 09/16/14 – slide 29
An example from the upcoming assignment . . .
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Tutorials
Read: Chap 4 09/16/14 – slide 29
An example from the upcoming assignment . . .
[back]
Tutorials
Read: Chap 4 09/16/14 – slide 29
The tutorial appears in its own window . . .
[back]
Tutorials
Read: Chap 4 09/16/14 – slide 29
The tutorial appears in its own window . . .
[back]
Tutorials
Read: Chap 4 09/16/14 – slide 29
Scoring . . .
Tutorials
Read: Chap 4 09/16/14 – slide 29
Scoring . . .
Tutorials
Read: Chap 4 09/16/14 – slide 29
Scoring of self-guided tutorials in assignmentsThe scoring in effect for each tutorial appears on its starting page, just below
the Part label. All tutorials are scored as follows:
50% credit = Working through all parts of the tutorial
50% credit = First answer to each question in the Exercises section.
[back]
Tutorials
Read: Chap 4 09/16/14 – slide 29
Click Submit when you are completely done
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