Transcript Force and Newton`s First Law

Scenario:
Three students, Fred, Tom and Bobby, are running in a 100
meter dash. It took Tom 10 seconds to run 50 meters, while
Bobby ran it in 12 seconds and Fred ran it in 15 seconds
Think --- Pair --- Share




Which student is running slower?
Which student will probably win the race?
Could another student still win the race?
Explain.
What are some other everyday examples of
speed, velocity and acceleration?
Activity
Ball’s trip to the Wall
Distance
(centimeters)
Time (seconds)
Speed
Forward or
Backward?
Velocity (+,-)
Speed
Forward or
Backward?
Velocity (+,-)
Ball’s trip from the Wall
Distance
(centimeters)
Time (seconds)
Physics
the study of the relationship between
matter and energy
Motion

A change in position in a certain amount of
time

Motion is relative. To know you are
moving, you must have a reference point

Distance – how far you traveled

Units for distance??
Distance vs. Displacement

The distance between the final position and
starting position is displacement

(Ex: hiking on a trail. The trail may be 1 mile
long but you may only end up 300 ft from where
you started)
Speed Equation


Speed – the distance traveled divided by the
time needed to travel that distance
SI Unit is meters per second (m/s)


Other Units?
Speed = distance
time
D
S
T
Practice
(Make sure you use the proper units)

If it takes you 3 hours to travel 60 miles, what
is your speed??

If you are running 3 miles in 30 minutes, what
is your speed?
Constant speed vs. Average speed

Constant speed – an object covers equal
distances in equal amounts of time

The speed of moving objects is not always
constant

Average speed: total distance
total time
Graphing Speed
Draw the Following Graph
Velocity

Velocity: Speed in a given direction


You can be going the same speed but two
different velocities
Velocity = distance + direction
time
D
V
T
Acceleration

The change in velocity divided by the time the
change occurs
A = Velocity(final) – Velocity(initial)
Time

Acceleration is speeding up, slowing down or
changing direction
Stop Here!!!
Day Two – Force!!!
Force

A force is a push or pull exerted on an object

Force is measured in Newtons (kg m/s2)
In order for an object to speed
up, slow down or change direction,
a force has to act on that object

Inertia is the object’s tendency
to resist changing its motion. The
more inertia, the harder it is to start
moving or slow it down

Total Force

Forces almost always act in pairs with one
force acting on either side of the object

The resulting force that exists between
two is the net force
Balanced Forces

Balanced forces exist when the total force is
equal to zero.

Balanced forces do not change an object’s
motion
Unbalanced Forces
When a net force acts on an object, they are said
to be unbalanced.
Unbalanced forces can cause an object to start
moving, stop moving, or change direction.
225 N
Net Force
Unbalanced
225 N
50 N
100 N
50 N
100 N
Net Force
Balanced
0N
792 N
632 N
100 N
1524 N
Net Force
Unbalanced
400 N
900 N
224 N
Friction and Air Resistance



Friction is the force between two objects in contact
that resists motion between two touching surfaces
It is what eventually causes things to slow down and
stop
Air Resistance is a form of friction between an
object and air molecules
Gravity



Gravity is the pull that all matter exerts on other matter
Gravity is dependent on the mass of an object and the
distance between the two objects
 The greater the mass, the more gravitational pull it will
have (i.e.: earth vs. moon)
 The greater the distance, the less gravitational pull it will
have
Mass vs Weight – weight is the amount of gravitational pull
on a person. So on the moon, your mass would be the same
but weight would be different
Free Fall and Terminal Velocity




When the only force acting on an object
is gravity, the object is said to be in free
fall
On earth, this is 9.8 m/s2 - Gravity
constant
In the absence of air resistance, all
objects on Earth accelerate at the same
rate, regardless of their mass.
An object reaches its terminal velocity
when the force of gravity is balanced by
the force of air resistance
Tuesday, November 9
Objective: Students will be able to: Practice problems about
What are
Force and Motion
you learning 1. Worksheet on Force and Motion
today?
2. Brainstorm ideas for project
Warm
Up
Read the
following:
Things
to do:
Sir Isaac Newton (4 January 1643 – 31 March 1727)was an English physicist,
mathematician, astronomer, natural philosopher, alchemist, and theologian, and
is considered by many scholars and members of the general public to be one of
the more influential people in human history. His Philosophiæ Naturalis
Principia Mathematica (Latin for "Mathematical Principles Of Natural
Philosophy"; usually called the Principia), published in 1687, is probably the
most important scientific book ever written. It lays the groundwork for most of
classical mechanics. In this work, Newton described universal gravitation and
the three laws of motion, which dominated the scientific view of the physical
universe for the next three centuries.
Take
out your notebook
Newton’s Laws
Newton’s First Law of Motion

“An object at rest will remain at rest and an

object in motion will maintain its velocity
unless it experiences an unbalanced force.”
This is often times called the law of Inertia
Newton’s Second Law of Motion



“The unbalanced force acting on an object
equals the object’s mass times its
acceleration”
F=ma
Force is measured in Newtons (kg m/s2)
Newton’s Third Law

For every action force, there is an equal and
opposite reaction force
In your notebook….

Draw or explain an example of each of
Newton’s 3 Laws.
Gravity Demo
Warm Up 11/16
Write Q&A

How much time does it take for a snail to
crawl 20 feet if he goes 2 feet/hr

Make sure you have turned in your speed
problems worksheet!!!
Warm Up 11/11




Get a calculator and begin calculate your
speeds for the 4 activities
Remember: Speed = Distance/Time
Round everything to the nearest hundreths
(ex. 5.45s)
Make sure and list your units in your answers
Warm Up 11/13

What is the formula for finding speed?

What is the formula for finding distance?

What is the formula for finding time?

Remember 2nd Law: F=MA
Warm Up 11/10
Write Q&A
 What
is speed?
 How do you calculate it?
Warm Up 11/4
Write Q&A

Write an example of something that goes
along with each of Newton’s Laws

Ex



1st - A car will sit at a stoplight until you press
the gas
2nd - It is harder to carry a box of rocks than a
box of popcorn
3rd - When birds fly, they push their wings
down in order to go up
Warm Up 11/4
 List
5 Examples of motion that
you see in your everyday
activities
Rubric for Project
Newton’s Laws Clips – 60 points total
Video Clip – 10 points
Description – 5 points
Does it fit law? – 5 points
Presentation – 15 points
Did all participate – 15 points
Creativity – 10 points
Wednesday, November 10
Objective: Students will be able to: demonstrate the everyday
What are
occurrences of Newton’s 3 laws
you learning 1. Video Project
today?
You must have 3 video clips by the end of the
class period!!
Warm
Up
Answer
the following:
Describe your interaction with one of Newton’s 3
laws in the last couple of days
Find
Things
to do:
a partner
Look at your drawings of the 3 laws from Monday
Monday, November 1
Objective: Students will be able to: Review the basics of the
What are
principles of Motion
you learning 1. Look at questions from Chemistry Test
today?
2. Notes on Motion
Warm
Up
Answer
the following: (Start a new section)
What evidence do you use to tell if you are in
motion or not?
Glue
Things
to do:
the notes into your spiral