Transcript PowerPoint Presentation - Newton’s Laws of Motion

BELL WORK
Week of Monday, March 23 – Friday, March 27
Thursday, March 26

Who is attributed with the discovery
of the three Laws of Motion?
WHAT’S HAPPENING IN AG?
THURS. 3/26
Announcements
Due Today – Newton’s Laws Webquest
Vocab Quiz – Friday, March 27 (TOMORROW)
FFA Meeting – Thursday, April 1
 Greenhand Degree Applications, Chapter Degree
Applications, and 2015-2016 Officer Applications will be
available
What are we doing today?
Lecture – Review Newton’s Laws
NEWTON’S LAWS OF
MOTION REVIEW
Intro to Agriculture
AAEC – Paradise Valley
Spring 2015
BACKGROUND
Sir Isaac Newton (1643-1727) an English
scientist and mathematician famous for his
discovery of the law of gravity also discovered
the three laws of motion. He published them in
his book Philosophiae Naturalis Principia
Mathematica (mathematic principles of natural
philosophy) in 1687. Today these laws are
known as Newton’s Laws of Motion and describe
the motion of all objects on the scale we
experience in our everyday lives.
“If I have ever made any valuable discoveries, it
has been owing more to patient attention, than
to any other talent.”
-Sir Isaac Newton
NEWTON’S LAWS OF MOTION
1. An object in motion tends to stay in motion and an
object at rest tends to stay at rest unless acted upon
by an unbalanced force.
2. Force equals mass times acceleration
(F = ma).
3. For every action there is an equal and opposite
reaction.
NEWTON’S FIRST LAW
An object at rest tends to stay at rest
and an object in motion tends to stay in
motion unless acted upon by an
unbalanced force.
WHAT DOES THIS MEAN?
Basically, an object will “keep doing what it was
doing” unless acted on by an unbalanced force.
If the object was sitting still, it will remain
stationary. If it was moving at a constant
velocity, it will keep moving.
It takes force to change the motion of an object.
BALANCED FORCES
Balanced Forces = forces that are equal in
size and in opposite directions (no
movement occurs)
UNBALANCED FORCES
Unbalanced Forces = the two forces are not
equal, so that there is a movement in one
direction.
NEWTON’S FIRST LAW IS ALSO CALLED THE LAW
OF INERTIA
Inertia: the tendency of an object to resist
changes in its state of motion
The First Law states that all objects have inertia.
The more mass an object has, the more inertia it
has (and the harder it is to change its motion).
Jenga is a game based on inertia. You try to move the
blocks without moving the other blocks. Eventually, the tower
becomes unbalanced.
NEWTON’S SECOND LAW
Force equals mass times acceleration.
F = ma
Acceleration: a measurement of how quickly
an object is changing speed.
WHAT DOES THIS MEAN?
F = ma basically means that the force of an object comes
from its mass and its acceleration.
Something very massive (high mass)
that’s changing speed very slowly (low
acceleration), like a glacier, can still
have great force.
Something very small (low mass) that’s
changing speed very quickly (high
acceleration), like a bullet, can still
have a great force. Something very
small changing speed very slowly will
have a very weak force.
PRACTICE PROBLEMS
1. If you push an object that
has a mass of 2 kg, and the
net force acting on the
object is 6N, what is the
object's acceleration?
2. If a mass of 5kg is moving
at an acceleration of 3
m/s2, what is the force?
In outer space, away from gravity and any
sources of friction, a rocket ship launched
with a certain speed and direction would
keep going in that same direction and at that
same speed forever.
WHAT IS GRAVITY?
Gravity = the attractive force between two
objects; depends on mass and distance
Earth’s Gravity
9.80665 m / s2
Moon’s Gravity
1.622 m/s²
NEWTON’S THIRD LAW
For every action there is an equal
and opposite reaction.
WHAT DOES THIS MEAN?
For every force acting on an object, there is an equal
force acting in the opposite direction. Right now,
gravity is pulling you down in your seat, but Newton’s
Third Law says your seat is pushing up against you with
equal force. This is why you are not moving. There is a
balanced force acting on you– gravity pulling down,
your seat pushing up.
MOMENTUM
Momentum describes how much force is
necessary to change an objects motion.
Which has more momentum:
A. soccer ball traveling at 5 m/s
B. a train traveling at 5 m/s
PRACTICE PROBLEMS
1. What is the momentum of a car with a
mass of 1000 kg traveling at the speed of 2 m/s?
2. A baseball has a momentum of 6 kg*m/s. If the mass
of the baseball is 3 kg, what is the baseball's velocity?
3. What is the mass of a person walking at a speed of
2 m/s if the person's momentum is 50 kg*m/s
VOCABULARY CHECK
Inertia: the tendency of an object to resist
changes in its state of motion
Acceleration: a change in velocity; a
measurement of how quickly an object is
changing speed, direction or both
Velocity: The rate of change of a position along
a straight line with respect to time
Force: strength or energy