# forces by qingyunliuliu

VIEWS: 20 PAGES: 87

• pg 1
```									     FORCES AND THEIR
EFFECTS
Unit 7K
Year 7 Science

Saturday, 23 July 2011                    1
Index
introduction
lesson 1: Are some magnets stronger than others?
lesson 2: What forces act on a parachute?
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, 23 July 2011                                          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, 23 July 2011                        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, 23 July 2011                                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, 23 July 2011                                     6
Lesson 1

Are some magnets stronger than
others?

Saturday, 23 July 2011                          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, 23 July 2011                      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, 23 July 2011                            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, 23
July 2011                                       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, 23 July 2011                                      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, 23 July 2011                           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

Saturday, 23 July 2011                                                  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, 23 July 2011                                     14
Lesson 2

What forces act on a parachute?

Saturday, 23 July 2011                           15
What forces act on a parachute?

Parachute video (it might work)

Saturday, 23 July 2011                  16
Equipment
•   Digital camera
•   A football
•   Parachutes
•   Timers
•   Whiteboards, pens & erasers
•   Study guides (3 levels differentiated)

Saturday, 23 July 2011                            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, 23 July 2011                           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, 23 July 2011                        19
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, 23 July 2011                                     20
Football photograph

• Trim and fix the photograph into your
book.
• Use arrows and straight lines to mark:
– Gravity
– Drag                      force called DRAG
To learn to draw
force diagrams
To learn how to
mark forces on a
Saturday, 23 July 2011               diagram       21
Next bit…
• DVD video input: BBC Class clips

Saturday, 23 July 2011                    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, 23 July 2011                                       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

• 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, 23 July 2011                              24
Finishing up
• Forces ‘Hammer & Feather on the
Moon’. (Class Clips DVD)

Saturday, 23 July 2011                   25
• Use your knowledge of DRAG to
explain why sports cars are streamlined.

HOMEWOK SHEET

Saturday, 23 July 2011                       26
to explain why sports cars are            to explain why sports cars are
streamlined.                              streamlined.
to explain why sports cars are            to explain why sports cars are
streamlined.                              streamlined.
to explain why sports cars are            to explain why sports cars are
streamlined.                              streamlined.
to explain why sports cars are            to explain why sports cars are
streamlined.                              streamlined.
to explain why sports cars are
Saturday, 23 July 2011   streamlined.                            27
Lesson 3

How much do balls bounce?

Saturday, 23 July 2011                          28
Getting started…

• Draw a ball falling. Think about its
shape.
• Draw a ball that has hit the ground and
its shape.

Saturday, 23 July 2011                       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, 23 July 2011                                    30
Which forces make balls
bounce?

1st
bounce

2nd
bounce

Saturday, 23 July 2011                     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, 23 July 2011                                    32
Results
test number   first bounce   second bounce

1

2

3

4

5

6

7

8

9

10

Saturday, 23 July 2011                                                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, 23 July 2011                        34
• 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, 23 July 2011                     35
Plenary & finishing off…
conclusion.
book. Improve it as you go.
• Homework: Complete the conclusion in

Saturday, 23 July 2011                      36
Forces & their effects: Lesson 4

Do rollers make it easier to drag
heavy things?

Saturday, 23 July 2011                              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, 23 July 2011                         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, 23 July 2011                                   39
Equipment

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

Saturday, 23 July 2011               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…
Saturday, 23 July 2011                                      41
Practical bit…

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

4

5

Saturday, 23 July 2011                                                  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?]
Saturday, 23 July 2011                      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, 23 July 2011                 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, 23 July 2011 PREVIOUS PAGE                              45
Forces & their effects:
Lesson 5
Why is iron heavier than
aluminium?

Saturday, 23 July 2011                              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, 23 July 2011                             47
Equipment
FOR GROUP USE
• Metal blocks (materials kit) Iron, brass,
• Electronic scales
• Study guides

Saturday, 23 July 2011                             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
Saturday, 23 July 2011                          49
brass

aluminium

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

Saturday, 23 July 2011                              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

Saturday, 23 July 2011                                 51
Material            Density (grams per cm3)

iron                7.87

brass               ?

aluminium           2.7

Saturday, 23 July 2011                             52
So…
Now you know which material
was the most dense.

Check learning

Saturday, 23 July 2011                53
Plenary: Any ideas?
Material            Density (grams per cm3)

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

Saturday, 23 July 2011                             54
Finishing up

•   Save any computer work.
Forces: Lesson 6

Are objects lighter under water?

Saturday, 23 July 2011                             56
Equipment
• Objects to weigh underwater
• Forcemeters

Saturday, 23 July 2011               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, 23 July 2011                                         58
What forces?
upthrust

thrust
drag

weight

Saturday, 23 July 2011                              59
The proper way…
upthrust

thrust                              drag

gravity
Saturday, 23 July 2011                     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, 23 July 2011                                61
Results
Object     weight in air   weight under    Difference
(NEWTONS)          water       (NEWTONS)
(NEWTONS)

Saturday, 23 July 2011                                                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, 23 July 2011                                            63
Conclusion & evaluation
• Explain why the objects were lighter
under water. Make sure you show your
knowledge of forces.

Saturday, 23 July 2011                        64
Forces: Lesson 7

Why are some toy cars faster than
others?

Saturday, 23 July 2011                           65
Equipment
•   Toy cars
•   Wooden ramps
•   Clinometers
•   Stop watches

Saturday, 23 July 2011   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, 23 July 2011                                      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, 23 July 2011                         68
Force diagram
holds
kart up

friction
and
drag
thrust

weight

Saturday, 23 July 2011                        69
Forces: Lesson 8

Do things float better in salty
water?

Saturday, 23 July 2011                                70
Equipment
•   Hydrometers
•   Salty water
•   Very salty water
•   Tap water
•   A ball
•   Transparent fish tank

Saturday, 23 July 2011           71
OBJECTIVES / OUTCOMES
• To learn about           • You can peruse,
forces that act in         choose and use the
right equipment.
different directions.
• You can measure
ability to explain why   • You can explain why
things happen.             forces make this
happen.
• You can evaluate your
test.

Saturday, 23 July 2011                                    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, 23 July 2011                        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, 23 July 2011                                       74
What if the ball was
lighter?

What if the water was
heavier?

How could you
make the water
heavier?
Saturday, 23 July 2011                          75
Input
• BBC DVD: Class Clips 1 / Materials &
their properties / Compounds &
mixtures / 5 Mixtures

Saturday, 23 July 2011                        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, 23 July 2011                                                                 77
Finishing up
• Why does the
hydrometer float
better in very salty
water? Write to
explain why in terms
of forces.

Saturday, 23 July 2011        78
Forces Lesson 9

Is friction sometimes useful?

Saturday, 23 July 2011                              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
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, 23 July 2011                               80
Equipment
• Video: Cycling crazy

Saturday, 23 July 2011        81
Activities
• Video: Cycling crazy
• High friction and low friction (use study
guide)

Saturday, 23 July 2011                             82
Saturday, 23 July 2011   83
Rounding up
that you know where high
friction is important.
that you know where low
friction is important.
• You can write useful
captions.

Saturday, 23 July 2011            84
Forces Lesson 10

Do pulleys help with lifting?

Saturday, 23 July 2011                               85
Equipment
•   Pulley sets
•   Hang on masses
•   Forcemeters
•   1kg masses
•   String

Saturday, 23 July 2011    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, 23 July 2011                                  87

```
To top