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forces

VIEWS: 14 PAGES: 87

									     FORCES AND THEIR
     EFFECTS
                             Unit 7K
                          Year 7 Science


Saturday, 14 April 2012                    1
     Index
    introduction
    lesson 1: Are some magnets stronger than others?
    lesson 2: What forces act on a parachute?
    Homework task 2
    lesson 3: How much do balls bounce?
    lesson 4: Do rollers make it easier to drag heavy things?
    lesson 5: Why is iron heavier than aluminium?
    lesson 6: Are objects lighter under water?
    lesson 7: Why are some toy cars faster than others?
    lesson 8: Do things float better in salty water?
    lesson 9: Is friction sometimes useful?
    lesson 10: Do pulleys help with lifting?

Saturday, 14 April 2012                                         3
     Forces
     • What are forces?
     • How do we measure forces?
     • How do we use forces in our ordinary
       lives?
     • How do forces affect our lives?



Saturday, 14 April 2012                       4
     What do all these terms mean?
     • FORCE: the influence that produces a
       change in a physical quantity; "force equals
       mass times acceleration" (Newtons)
     • POWER: the rate of doing work; measured in
       watts (joules per second)
     • WORK: "work equals force times distance"
     • ENERGY: the capacity of a physical system
       to do work (joules)

Saturday, 14 April 2012                               5
Introduction
     Getting help
              You will be loaned a study guide

              Use our web site


     This unit is all about FORCES
     pushes, pulls and twists
     Forces are measured in NEWTONS

       http://www.westwightmiddle.iow.sch.uk/science.htm
Saturday, 14 April 2012                                    6
     Lesson 1

               Are some magnets stronger than
                         others?



Saturday, 14 April 2012                         7
     Objectives
     and what I am looking for
• Learn about             • Learn how to use
  magnetic force            the guide mats
• Learn to list the key   • Make a proper
  variables effectively     variables list
• Learn to evaluate       • Record your results
  the way you work          in a table
• Make careful
  measurements.
Saturday, 14 April 2012                     8
     Equipment
     •   A variety of different magnets
     •   30 cm rules marked in mm
     •   Steel ball bearings
     •   Results tables
     •   Level mats
     •   Study guides (3 levels differentiated)



Saturday, 14 April 2012                           9
Are some magnets              Learn to list the key
                              variables effectively
stronger than others?         Learn to evaluate the
                              way you work
                              Make careful
                              measurements.




                        • Watch a demonstration
                        of how to test.
                        • What are variables?
                        • Use whiteboards to list
                        the variables.

Saturday, 14
April 2012                                      10
Are some magnets                           Learn to list the key
                                           variables effectively
stronger than others?                      Learn to evaluate the
                                           way you work
                                           Make careful
New page. Date and title in your book.     measurements.


        Planning

        1. Make a list of the key
           variables
        2. Which variable will you test?
        3. Which variable will you
           measure?
        4. Which variables will you keep
           the same?
Saturday, 14 April 2012                                      11
                               Learn to list the key
Are some magnets               variables effectively
stronger than others?          Learn to evaluate the
                               way you work
                               Make careful
                               measurements.


 • Put the ball bearing on the table.
 • Move the magnet nearer to the ball bearing.
 • How close was the magnet when the ball
   started to move? Measure.
 • Record your results and try again with a
   different magnet.

Saturday, 14 April 2012                          12
                                                      Learn to list the key
Are some magnets stronger                             variables effectively
than others?                                          Learn to evaluate the
                                                      way you work
                                                      Make careful
                                                      measurements.
Let’s share our results
        Magnet            How close was the magnet?




                                                         Observations
                                                         State which
                                                         magnet is the
                                                         strongest
                                                         according to
                                                         your results.

Saturday, 14 April 2012                                                 13
                                          Learn to list the key
Are some magnets                          variables effectively
stronger than others?                     Learn to evaluate the
                                          way you work
                                          Make careful
                                          measurements.

                          Work in pairs
     Evaluation
     • How well did your test go?
     • Did you feel that your results were accurate?
     • How could you have improved your test in
       order to get more accurate results or results
       you could have been more sure of?


Saturday, 14 April 2012                                     14
     Lesson 2

                What forces act on a parachute?




Saturday, 14 April 2012                           15
     What forces act on a parachute?

      Parachute video (it might work)




Saturday, 14 April 2012                 16
     Equipment
     •   Digital camera
     •   A football
     •   Parachutes
     •   Timers
     •   Whiteboards, pens & erasers
     •   Study guides (3 levels differentiated)

Saturday, 14 April 2012                           17
     OBJECTIVES
     & what I am looking for
     • To learn about a    • Make a diagram that
       force called DRAG     clearly shows the
     • To learn to draw      forces that act on it.
       force diagrams      • Write to describe
                             which force is
     • To learn how to       largest.
       mark forces on a
                           • Write to explain how
       diagram               you know.

Saturday, 14 April 2012                          18
How to mark force                  To learn about a
                                   force called DRAG

arrows on diagrams.                To learn to draw
                                   force diagrams
                                   To learn how to
                                   mark forces on a
                          lift     diagram




                                        drag

                thrust
                                   New page, date
                                   & title.
                          weight
                                   Copy the
                                   diagram.
Saturday, 14 April 2012                        19
                                              To learn about a
Football                                      force called DRAG
                                              To learn to draw
                                              force diagrams
                                              To learn how to
                                              mark forces on a
                                              diagram


                          • We will go into the
                            playground to watch a
                            football and bring back a
                            photograph.



Saturday, 14 April 2012                                     20
Football photograph


    • Trim and fix the photograph into your
      book.
    • Use arrows and straight lines to mark:
          – Gravity
                                     To learn about a
          – Drag                     force called DRAG
                                     To learn to draw
                                     force diagrams
                                     To learn how to
                                     mark forces on a
Saturday, 14 April 2012              diagram       21
     Next bit…
     • DVD video input: BBC Class clips




Saturday, 14 April 2012                   22
Plenary: What                                    To learn about a
                                                 force called DRAG

forces act on a                                  To learn to draw
                                                 force diagrams

parachute?                                       To learn how to
                                                 mark forces on a
                                                 diagram



       Work in pairs
                                                       HOMEWORK

•   Try a parachute in the lab from a height of exactly 2 metres.
•   NOW RECORD THIS ON YOUR GROUP’S WHITEBOARD
•   Decide what force pulls the parachute down.
•   Decide what force holds the parachute up.
•   Which of the forces was greatest? Explain how you know.

Saturday, 14 April 2012                                      23
What forces act on                      To learn about a
                                        force called DRAG

a parachute?                            To learn to draw
                                        force diagrams
                                        To learn how to
                                        mark forces on a
   IN YOUR BOOK                         diagram

     • The force that pulls the parachute down is…
     • The force that holds the parachute up is.
     • Draw an accurate 2d diagram that shows the
       parachute and the two forces acting on it.
     • The force that was greatest was… I know
       this because…


Saturday, 14 April 2012                             24
     Finishing up
     • Forces ‘Hammer & Feather on the
       Moon’. (Class Clips DVD)




Saturday, 14 April 2012                  25
     Homework task 2
     • Use your knowledge of DRAG to
       explain why sports cars are streamlined.




HOMEWOK SHEET

Saturday, 14 April 2012                      26
Use your knowledge of DRAG                 Use your knowledge of DRAG
to explain why sports cars are             to explain why sports cars are
streamlined.                               streamlined.
Use your knowledge of DRAG                 Use your knowledge of DRAG
to explain why sports cars are             to explain why sports cars are
streamlined.                               streamlined.
Use your knowledge of DRAG                 Use your knowledge of DRAG
to explain why sports cars are             to explain why sports cars are
streamlined.                               streamlined.
Use your knowledge of DRAG                 Use your knowledge of DRAG
to explain why sports cars are             to explain why sports cars are
streamlined.                               streamlined.
                           Use your knowledge of DRAG
                           to explain why sports cars are
 Saturday, 14 April 2012   streamlined.                            27
     Lesson 3

                    How much do balls bounce?




Saturday, 14 April 2012                         28
     Getting started…

     • Draw a ball falling. Think about its
       shape.
     • Draw a ball that has hit the ground and
       is about to bounce back up. Think about
       its shape.


Saturday, 14 April 2012                      29
     OBJECTIVES
     & what I am looking for
   • How do forces make        • Be able to do a test and
     things bounce?              make accurate
   • Are my measurements         measurements.
     accurate?                 • Be able to repeat
                                 measurements to check.
   • Why is it important to
     repeat my tests?          • Be able to clearly describe
                                 what happened.
   • How can I use my
                               • Be able to use your
     scientific knowledge to
                                 knowledge to explain how
     explain?                    and why things happen.


Saturday, 14 April 2012                                   30
     Which forces make balls
     bounce?

                            1st
                          bounce



                                    2nd
                                   bounce




Saturday, 14 April 2012                     31
                            Equipment



     Equipment
     • Clamp stand with
                                            table tennis ball
       clamp and boss.
     • Metre rule.            clamp stand
     • Table tennis ball.
     • Results table.          metre
                               rule
     • Study guides.



Saturday, 14 April 2012                                   32
Results
                          test number   first bounce   second bounce


                              1


                              2


                              3


                              4


                              5


                              6


                              7


                              8


                              9


                              10




Saturday, 14 April 2012                                                33
     Conclusion
     • According to your results, describe what
       happened.
     • Use your understanding to explain why
       the first bounce was more than the
       second bounce.



Saturday, 14 April 2012                       34
     Something to think about…
     • The falling ball had kinetic energy
       because it was moving.
     • The amount of movement got less after
       the first bounce.
     • So, where did the kinetic energy go?



Saturday, 14 April 2012                    35
     Plenary & finishing off…
     • Your group might be asked to read your
       conclusion.
     • Copy your conclusion to your exercise
       book. Improve it as you go.
     • Homework: Complete the conclusion in
       your book.


Saturday, 14 April 2012                     36
 Forces & their effects: Lesson 4

                Do rollers make it easier to drag
                         heavy things?



Saturday, 14 April 2012                             37
     Just for starters…
     • Draw a picture of a bloke dragging a
       heavy rock.
     • Draw a picture of the same bloke
       dragging a heavy rock using rollers.



      •Can you show which one is the hardest
      work?
Saturday, 14 April 2012                        38
     OBJECTIVES
     & what I am looking for
     • To learn how to          • Know about control,
       write why your test        independent and
                                  dependent variables.
       is fair.
                                • Write a useful
     • To learn how to            prediction.
       make a useful bar        • Record your results
       chart.                     accurately.
     • To extend your           • Write to explain why
       ability to explain why     things happened.
       things happen.           • Write an evaluation.
Saturday, 14 April 2012                                  39
     Equipment



                          FOR GROUP WORK:
                          • Dowel rollers
                          • Force meters
                          • String
                          • A brick
                          • Study guiders
                          • Results tables
                          • Level mats




Saturday, 14 April 2012               40
     Key variables
     INDEPENDENT VARIABLE
       The variable I will test is…
     DEPENDENT VARIABLE
       The variable I will measure is…
     CONTROL VARIABLES
       The variables I will keep the same are…
                          Redraft into your exercise book.
Saturday, 14 April 2012                                      41
     Practical bit…

                          RESULTS
                             Test number   How much force     How much force
                                           without rollers?    with rollers?
    Use a board                  1
    to protect                   2
    your bench.                  3

                                 4

                                 5




Saturday, 14 April 2012                                                  42
     Conclusion


     • Produce a graph that shows these
       results clearly. [What should my graph
       look like?]
     • Write to explain what happened in terms
       of forces and energy. [What should my
       work look like?]
     • Plenary: Evaluate your test.
Saturday, 14 April 2012                     43
    A clear graph
                         16
                         14
                         12
                                                               1
                         10
                                                               2
             Force (N)




                          8
                                                               3
                          6
                                                               4
                          4
                                                               5
                          2
                          0
                              Without rollers   With rollers


                      CONCLUSION
Saturday, 14 April 2012                PAGE                        44
    Model conclusion
        If the brick is dragged along the ground, the rough
        surfaces lock together and make lots of friction.
        All of the surface of the brick is touching the ground.
        The bigger the surface, the more friction there is.
        It takes a lot of force to drag the brick.


        If you use rollers, the rough surfaces do not lock
        together and so there is much less friction. So it takes
        much less force to pull the block.

Saturday, 14 April 2012 PREVIOUS PAGE                             45
     Forces & their effects:
     Lesson 5
                          Why is iron heavier than
                                aluminium?



Saturday, 14 April 2012                              46
      OBJECTIVES
      & what I am looking for
     • To learn the idea of   • You can measure
       density.                 mass in grams.
     • To learn to measure    • You can measure
       and compare              volume in cm³ .
       different materials.   • You can record your
                                results in tables.
                              • You can calculate
                                the mass of 1 cm³ of
                                each material.

Saturday, 14 April 2012                            47
     Equipment
     FOR GROUP USE
     • Metal blocks (materials kit) Iron, brass,
       aluminium & lead HAZARD
     • Electronic scales
     • Study guides



Saturday, 14 April 2012                            48
     Stage 1
    • What is the mass of each metal block?
      (Measure in grams)
    • Make a table of your results.
                            metal      mass g
                             iron
                            brass
                           aluminium
                             lead
Saturday, 14 April 2012                         49
     Was this a fair comparison?
                              brass

                  iron                lead




                          aluminium




            • Describe why your test is not fair.
            • Can you work out what the mass
              would be if every block was 1 cm³?

Saturday, 14 April 2012                             50
     What is the mass of 1cm3 ?
     • Can you work out what the mass would be if
       every block was 1 cm³?

       Material           Mass (g)   Volume   Density
                                     (cm3)    (g/cm3)
       iron

       brass

       aluminium

       lead


Saturday, 14 April 2012                                 51
     What should your results be?
     Material             Density (grams per cm3)

     iron                 7.87

     brass                ?

     aluminium            2.7

     lead                 11.36

Saturday, 14 April 2012                             52
     So…
     Now you know which material
      was the most dense.



                          Check learning

Saturday, 14 April 2012                53
     Plenary: Any ideas?
     Material             Density (grams per cm3)

     iron                 7.87
     brass                ?
     aluminium            2.7
     lead                 11.36
     water?
     Copper?
     Wood?
     Cheese?


Saturday, 14 April 2012                             54
Finishing up

•   Save any computer work.
•   Equipment away please.
•   Give in your books.
•   Clear your table.
•   WASH YOUR HANDS!
     Forces: Lesson 6

                Are objects lighter under water?




Saturday, 14 April 2012                            56
     Equipment
     • Objects to weigh underwater
     • Forcemeters




Saturday, 14 April 2012              57
    OBJECTIVES
    & what I am looking for
     • To learn the idea of a     • You can draw a basic force
       force called upthrust.       diagram in 2D.
                                  • You are able to measure
     • To learn how to make         force accurately using a
       accurate measurements        force meter.
       of forces.                 • You can use the computer to
     • To develop your ability      produce a useful graph that
       to explain why things        shows your results clearly.
       happen.                    • You can explain why forces
                                    cause things to be lighter in
     • To correctly mark forces     water.
       on diagrams.               • You can evaluate your test.


Saturday, 14 April 2012                                        58
     What forces?
                                   upthrust




        thrust
                                              drag




                          weight




Saturday, 14 April 2012                              59
 The proper way…
                          upthrust




thrust                               drag




                          gravity
Saturday, 14 April 2012                     60
     Instructions
     • Use the study guide. Write the title & date.
     • Write: What is the force that pulls down on
       the stone? [The force that… ]
     • Draw the diagram in 2 dimensions showing
       the forces correctly.
     • Use the equipment to find out if objects are
       lighter under the water. Repeat each test to
       get accurate results.
     • Record your results in a table.

Saturday, 14 April 2012                               61
     Results
               Object     weight in air   weight under    Difference
                          (NEWTONS)          water       (NEWTONS)
                                          (NEWTONS)




Saturday, 14 April 2012                                                62
     Produce a spreadsheet using a computer. Use
     a formula to calculate the difference column.
            Object        weight in air   weight under    Difference
                          (NEWTONS)          water       (NEWTONS)
                                          (NEWTONS)


             stone             3              2          =B2-C2
          iron block           5             3½




Saturday, 14 April 2012                                            63
     Conclusion & evaluation
     • Explain why the objects were lighter
       under water. Make sure you show your
       knowledge of forces.
     • Evaluate your test.




Saturday, 14 April 2012                       64
     Forces: Lesson 7

              Why are some toy cars faster than
                         others?



Saturday, 14 April 2012                           65
     Equipment
     •   Toy cars
     •   Wooden ramps
     •   Clinometers
     •   Stop watches




Saturday, 14 April 2012   66
     OBJECTIVES
     • To learn why it is        • To do a fair test.
       important to make lots    • To learn why it is
       of measurements.            important to make lots
     • To learn how to explain     of measurements.
       why things happen.        • To explain why a force
     • To learn about friction     called friction affects the
       and drag.                   speed of a car.
                                 • To explain what
                                   happens to the energy.
                                 • To calculate speed.
Saturday, 14 April 2012                                     67
     By the end of the lesson…
     • Be able to peruse, choose and use the
       right equipment.
     • Be able to list the variables.
     • Be able to write an explanation.
     • Be able to measure and calculate
       speed.*


Saturday, 14 April 2012                        68
     Force diagram
                          road
                          holds
                          kart up




                                    friction
                                    and
                                    drag
  thrust



                           weight



Saturday, 14 April 2012                        69
     Forces: Lesson 8

                    Do things float better in salty
                               water?



Saturday, 14 April 2012                               70
     Equipment
     •   Hydrometers
     •   Salty water
     •   Very salty water
     •   Tap water
     •   A ball
     •   Transparent fish tank

Saturday, 14 April 2012          71
     OBJECTIVES / OUTCOMES
     • To learn about           • You can peruse,
       forces that act in         choose and use the
                                  right equipment.
       different directions.
                                • You can measure
     • To develop your            accurately.
       ability to explain why   • You can explain why
       things happen.             forces make this
                                  happen.
                                • You can evaluate your
                                  test.

Saturday, 14 April 2012                                   72
     Starter
     Pushing a ball onto a bucket of water.

     Key questions…
     • As I push the ball down, what happens
        to the water?
     • Does the water have mass? Am I
        lifting it?
Saturday, 14 April 2012                       73
As the ball is pulled
down by gravity, the
water is lifted.




                   The ball will go down until it balances
                   the mass of the water it is pushing out
                   of the way.


Saturday, 14 April 2012                                      74
                          What if the ball was
                          lighter?


                            What if the water was
                            heavier?


                                How could you
                                make the water
                                heavier?
Saturday, 14 April 2012                          75
     Input
     • BBC DVD: Class Clips 1 / Materials &
       their properties / Compounds &
       mixtures / 5 Mixtures




Saturday, 14 April 2012                       76
    VERY
   SALTY
   WATER      SALTY        TAP
              WATER       WATER
                                               diagram          •Use the same
                                                                hydrometer every
                                                                time.
                                               Wooden
                                               dowel
                                                                •Measure how high
                                                                the hydrometer floats
                                               blob of          (in mm from the
                                               plasticine       surface of the water
                                                                to the top of the
                                             water              dowel).

                                          Water type            Height of     Density of water
                                                            hydrometer (mm)

                                  Very salty

                                  Salty

                                  Tap water (no salt)
Saturday, 14 April 2012                                                                 77
     Finishing up
     • Why does the
       hydrometer float
       better in very salty
       water? Write to
       explain why in terms
       of forces.
     • Evaluate your test.

Saturday, 14 April 2012       78
     Forces Lesson 9

                    Is friction sometimes useful?




Saturday, 14 April 2012                             79
     OBJECTIVES / OUTCOMES
     • To learn how friction   • Your two diagrams
       is sometimes a            show that you know
       useful force.             where high friction is
                                 important.
     • To learn where
                               • Your two diagrams
       friction forces           show that you know
       happen.                   where low friction is
     • To learn how to add       important.
       labels and captions.    • You can write useful
                                 captions.
Saturday, 14 April 2012                              80
     Equipment
     • Video: Cycling crazy




Saturday, 14 April 2012       81
     Activities
     • Video: Cycling crazy
     • High friction and low friction (use study
       guide)




Saturday, 14 April 2012                            82
Saturday, 14 April 2012   83
     Rounding up
     • Your two diagrams show
       that you know where high
       friction is important.
     • Your two diagrams show
       that you know where low
       friction is important.
     • You can write useful
       captions.

Saturday, 14 April 2012           84
     Forces Lesson 10

                      Do pulleys help with lifting?




Saturday, 14 April 2012                               85
     Equipment
     •   Pulley sets
     •   Hang on masses
     •   Forcemeters
     •   1kg masses
     •   String



Saturday, 14 April 2012   86
     OBJECTIVES/ OUTCOMES
     • To learn that pulleys      • You can work as a team
       are helpful for lifting.     to set up the test.
                                  • You can use a
                                    forcemeter to measure
                                    the pulling forces.
                                  • You can record your
                                    results in a table.
                                  • You can write to
                                    describe what you
                                    noticed.

Saturday, 14 April 2012                                 87

								
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