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Force and Newton

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Title: Force and Newton s First Law Author: kboyse Last modified by: Joshua Harden Created Date: 9/27/2007 9:09:34 PM Document presentation format – PowerPoint PPT presentation

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Title: Force and Newton


1
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
2
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?

3
Activity
Balls trip to the Wall Balls trip from
the Wall
Distance (centimeters) Time (seconds) Speed Forward or Backward? Velocity (,-)

Distance (centimeters) Time (seconds) Speed Forward or Backward? Velocity (,-)

4
Physics the study of the relationship between
matter and energy
5
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??

6
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)

7
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

8
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?

9
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

10
Graphing Speed
11
Draw the Following Graph
12
Velocity
  • Velocity Speed in a given direction
  • You can be going the same speed but two different
    velocities
  • Velocity distance direction
  • time

D
T
V
13
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

14
Stop Here!!!
15
Day Two Force!!!
16
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 objects tendency
  • to resist changing its motion. The
  • more inertia, the harder it is to start
  • moving or slow it down

17
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

18
Balanced Forces
  • Balanced forces exist when the total force is
    equal to zero.
  • Balanced forces do not change an objects motion

19
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.

20
Problem A
225 N
225 N
Net Force
Unbalanced
21
Problem C
50 N
100 N
50 N
0 N
Net Force
100 N
Balanced
22
Problem D
792 N
400 N
632 N
900 N
100 N
224 N
1524 N
Net Force
Unbalanced
23
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

24
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

25
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

26
Tuesday, November 9
Objective What are you learning today?
  • Students will be able to Practice problems
    about Force and Motion
  • Worksheet on Force and Motion
  • Brainstorm ideas for project

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.
Warm Up
Read the following
Things to do
  • Take out your notebook

27
Newtons Laws
28
Newtons 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

29
Newtons Second Law of Motion
  • The unbalanced force acting on an object equals
    the objects mass times its acceleration
  • Fma
  • Force is measured in Newtons (kg m/s2)

30
Newtons Third Law
  • For every action force, there is an equal and
    opposite reaction force

31
In your notebook.
  • Draw or explain an example of each of Newtons 3
    Laws.

32
Gravity Demo
33
Warm Up 11/16 Write QA
  • 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!!!

34
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

35
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 FMA

36
Warm Up 11/10 Write QA
  • What is speed?
  • How do you calculate it?

37
Warm Up 11/4 Write QA
  • Write an example of something that goes along
    with each of Newtons 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

38
Warm Up 11/4
  • List 5 Examples of motion that you see in your
    everyday activities

39
Rubric for Project
Newtons 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
40
Wednesday, November 10
Objective What are you learning today?
  • Students will be able to demonstrate the
    everyday occurrences of Newtons 3 laws
  • Video Project
  • You must have 3 video clips by the end of the
    class period!!

Warm Up
  • Answer the following
  • Describe your interaction with one of Newtons 3
    laws in the last couple of days
  • Find a partner
  • Look at your drawings of the 3 laws from Monday

Things to do
41
Monday, November 1
Objective What are you learning today?
  • Students will be able to Review the basics of
    the principles of Motion
  • Look at questions from Chemistry Test
  • 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 the notes into your spiral

Things to do
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