unit 2 force and movement - talİm terbİye...
TRANSCRIPT
UNIT 2 FORCE AND MOVEMENT
Dynomometer
Weight
is measured
by
means
Gravity
Upthrust
Electrical Force
Magnetic Force
Resultant
Frictional Force
FORCE
in used
for
Motion is
opposite with
causes
is done by
Work
Simple Machines
vectorial scalar
SpeedVelocity
MOVEMENT
20
Anything we throw upwards falls back
down but none of the hunderds of satellites in
space fall down. What is the reason for this?
Discuss this with your friends and note
your answers in your notebooks. Go over your
answers after you finish the unit.
Entry Activities
When historical buildings were constructed many years ago there were no working machines
like excavators or cranes.Therefore how were the huge and heavy stones used in buildings moved or
lifted up.
Discuss this with your friends and note your answers in your notebooks. Go over your answers
after you finish the unit.
2
21
We get up in the morning open the bedroom door, slice bread put the book on our desk into our
schoolbag and so on. We live our lives by performing many actions of this kind. Have you noticed that
these activities are all or actions.pushing pulling
We can see that a huge ship is pushed by its motors, or can observe how the wind moves the
leaves around.In both cases, what we see is not the force, but it is the results brought about by
force.In most general terms, force is the pushing or pulling action.We can understand the presence of
force by seeing or feeling the results it brings about.
We open the lid of a jar by exerting
and we pull a weight by exerting
There are two types of force;The one with a circular effect is the circular force and the
one that forms a linear effect is the linear force. circular force
linear force.
FORCE AND MOVEMENT
Force and Movement
22
� The Stone we throw upwards falls back down.
�
�
�
We open our bedroom window by pushing it.
Magnets attract (pull) metals like iron and nickel.
We carry weights from one place to another either by pulling or by pushing them.
2.1 A - Forces in our Environment
If we let the stone in our hand go, it falls down. Is this caused
by a force. Yes it is caused by the force of attraction . All the
objects exert a force on one another, but the force exerted by small
objects on one another is so small that it is negligible. However, the
earth is so huge that, the force it exerts is large enongh to pull all the
other objects to itself. This force is called the . Water and air
have the effect of lifting objects upwards, i.e. they have the buoyant
force.
gravity
Upthrust of Water
Magnets attract some metals. There is rejection (pushing) or attraction (pulling) between
magnets as well. This is called the There is a similar attractions in an atom, this is
called the .
magnetic force.
electrical force
The unit of force is named
after the
scientist that found the Law
of General Attaction.
Sir Isaac Newton,
Did You Know?
2
Upthrust of Air
( Force of air resistance)
Gravity Gravity
23
2.1 B - What is Force ?
When playing football, we send the ball to different
directions, to our teammates or to the nets to score a goal.
The ball gains different speeds according to the force we
exert on it. It stops when the goal keeper catches it.
When playing the “rope pulling” game, the team which
pulls with a greater force, wins. If both teams pull with the
same force , none of the teams wins as there will be no
movement. The force used here is the force in our muscles.
Different forces act on an object in different directions. If the
object is stationary, then, all the opposite forces acting on it are
balanced. In order for the object to move, the force in one direction
must be greater than the force acting on it in the opposite direction
.
.
Force can move stationary objects, can stop moving objects or can
change the direction of movement
100 Newton 100 Newton
Opposing forces are balanced, the object does not move.
20 Newton 100 Newton The right hand force is greater; 100-20=80N .
The object moves to right with a force of 80N.
100 Newton 100 NewtonThe total force to the left is greater;
(100+20) - 100 = 20N. The object moves to left with a
force from of 20N
Opposing forces (to the right and to the left) are
balanced, but as there is another force from another
direction, the object moves downwards.
100 Newton 100 Newton
100 Newton
20 Newton
The billiard robot designed in
Bristol University,England, can
calculate the exact force that
should be used to hit the balls.
Force and Movement
Did You Know?
24
We know that objects have mass and volume and that mass can be measured by using a scale.We
now learned that one of the greatest forces acting on objects is the . Scientists
prepared a scaled apparatus with a spring and decided that the amount of stretching of a 100gr object
on this apparatus is equql to a force of .This apparatus is called a .
A dynomometer can be prepared in various forms.A manual scale with a spring is a
dynomometer. The maximum amount of force that can be measured by laboratory dynomometers have
a limited stretching capacity. Stretching capacity of the spring determines the amount of force that
can be measured by that dynamometer.
Granitational Force
1 Newton dynamometer
2.1 C - How Do We Measure Force?
The gravitational force acting on a 1 kg object on earth
is approximately 9.81Newtons.
Thus, we can calculate the weight of a 20 kg (mass)
object is 20 x 9.81=196.2 Newtons.Gravitational
Force
As can be seen from the given example is exerted on objects by
earth. An astraunot on the moon has a smaller weight than he has on earth as the gravitational force on
the moon is smaller than that on earth .In space, the astraunot has no weight as there is no
gravitational force in space.
Therefore;
.
weight the gravitational force
it can be stated that each object has a constant mass but its weight changes
according to the gravitational force in different environment
Activity
After studying the pictures above, draw
the force(s) acting on objects, and state
which one(s) are balanced.The gravitational force on
the moon is 1/6 th of that
on earth.
2
Did You Know?
25
2.2 A - Forces in Action
I spent the day moving a stone out of our garden. I tied a rope
around the stone and dragged it out. Finally, I did it. I got rid of the
stone but I had a tiring work day.
I wish the stone was closer to the fence,then I could move it
outside much easily and would have a less tiring workday . However, the
stone was very far from the fence and I had to put a lot of effort in
order to move it outside.
As given in the example above, scientists call
. If the object does not move in the direction of force we apply, then we do not do any
work.
“the force applied times the distance moved by
the object” work
WORK = FORCE x DISTANCE
Force: 100 Newton
Distance: 15 meterJoule Newton Meter
WORK = 100 x 15 = 1500 Joule
If I was stronger, I could move the stone out much faster. Then I would not have to spend the
whole day working.
Scientists call the speed of work done .Power is the time taken to do the work.power
WORKPOWER =
TIME
________
Watt
Second
Joule
The unit of power which was
previously stated as horse
power is named after
the creator of steam
machine.
James
Watt
People evaluate the power spent for work.
This is one of the fundamental principles of the
Declaration of Human Rights
Force and Movement
Did You Know?
26
Kyrenia Castle and Salamis ancient city are the
examples of architecture that have remained from
ancient times. Pyramids in Egypt are other examples of
architecture from old times. How were these ancient
buildings constructed at that time? How were these
ancient buildings constructed at times when there
were no modern machinery?Lenght of the slope
is 800 meters
Height
is
100
meters
The largest pyramid is about 146 meters high. Large rocks used in building the pyramids were
taken to a height of 146 meters by inclined planes or ramps.
Lifting the rock directly upwards involves movement in a shorter distance, butit requires a
much greater force. When it is carried by using an inclined plane, it has to be moved it is much smaller.
A rock that would need thousands of men to be lifted can be brought to the same height by a
few men.
Using an inclined plane does not change the amount of work done, but the same weight is carried
over a much longer distance. The larger distance in using an inclined plane, the smaller the force
required. This is an example of a basic machine. Scientists name the basic machines that can change
the type of force, the direction or the magnitude of force, as simple machines.
100 1
= ------- = ---
800 8
Gained
Force
The Greek scientist Heron who
lived in the 2nd century
believed that even the most
complex machines consists of 5
simple machines.
2.3 A - Simple Machines2
Scientific ideas make
your life easier.
Did You Know?
27
2.3 B - Inclined Planes In Our Environment
Inclined Plane
Inclined planes are the simplest machines used for many puposes.
The front part of a ship Works as an inclined plane. It is
because of this inclined planet hat the ship uplits water and
moves along easily.
An ax is a machine that has two
incline planes brought together.
The sharp edge of the ax hits the
tree bark, and with its gradually
wideniry structure the tree into
two.
Screw
screw
step.
A screw, which has a wide variety of uses, holds two or more
pieces together. Screws change the circular force into linear
force. Altought a screw does not resemble an inclined plane, it
Works like one.
When a screw makes a
complete turn, it moves a thead
space. This is called a
Activity
Find 5 different inclined planes in your environment and
state the use of each one of them.
The ziper, invented in 1891 by an
American cal led Whitcomb
Judson, is a simple machine that
Works with the help of three
inclined planes.
Force and Movement
Did You Know?
28
Lever
Levers are simple machines that consist of a rod and a support. According to the purpose of
using the lever, the support can be placed any where below the rod.
We use various levers in our everyday life. Fishing line, hammer scissors, balance(scale) are all
examples of levers.
2.3 C - We Are Lifting Heavy Weights With Small Forces
Effort
Effort Distance
PivotLoad Distance
Pulley
Fixed pulleys, movable pulleys and pulley systems
We can change the direction and magnitude of a force by using a
pulley. Elavators and cranes that do the lifting actions use pulleys. Pulleys
are divided into three: .
WeightWeightForce
Pulley System
Activity: Show the place of
pivot, force and load points on
each of the following levers.
In sailing ships, pulleys are
used in folding and unfolding
the sails faster and easier.
2
Did You Know?
Fixed pulley Movable pulley
Force
Force
Weight
Load
29
2.3 D - Let Us Use the Rotational Force
Wheel and Axle
Wheel is one of the most important inventions. Vehicles move by the movement of an axle that
is turned by wheels. The circular movement of the axle is changed into a linear movement by the wheel.
As the cirumference of the wheel is much greater than that of the axle, the force exerted by the axle
on the wheel is much greater than the force exerted by the wheel on the ground.
The handle of a screwdriver is wider than its
axle. Therefore, the screw can be rotated with a
greater force. Screwdriver is a good example of
a wheel and axle.
Big area
low force
Little are
high force
Gear and Wheels
Wheels with teeth or with belts are simple machines that change
the magnitude and direction of force.
Wheels that rotate are connected to each other by teeth or by a belt.As
a result, the rotation of one wheel causes the rotation of the other.
When the larger wheel makes 1 complete turn, the smaller wheel makes 2
or more rotations.
Wheels with teeth or with belts are used in bicycles.
Chains, instead of belts, increase the strength of the
connection.
Gear
Wheel
Activity
By looking at the diagram aside,
make a wheel with teeth. For this,
you need a 1 cm thick potatoe slice,
a cardboard box and 16 toothpicks. The smallest motor produced
in the world was made by
Toshiba and it is in
width.
1 mm
Force and Movement
Did You Know?
30
� When we hit a ball, it moves, but it gradually slows down and stops.
If we push a book on the table, it slows down and stops after a while.
Any object we apply a force on slows down and stops after moving for a while. Why is this so?
. We learned this statement before. Then, it is a type of force which stops a
moving object. Which one? This force is the , As the frictional force opposes the
movement of the object, it stops the object.
�
Force can cause the movement of a stationary object, can stop moving objects or learned the
direction of movement
friction force
2.4 A - If There was no Friction!
Force Applied
Motion
Frictional Force
Let us rub our hands together, what happens?Our hands get warmer.If we continue to rub our
hands, friction causes wear and our hands are hurt.
Friction leads to loss of power, because some of the energy we use changes into heat energy due
to friction, and it is lost.
The frictional force affects the moving vehicles. Scientists have been working on a new vehicle
design called aerodynamics in order to reduce friction caused by air.
The frictional force affects the moving vehicles.
Scientists have been working on a new vehicle design
called aerodynamics in order to reduce friction caused by
air.
Friction has some uses. If there was no friction between our
feet and ground, we would not be able to walk, we would slide and fall.
That is why shoes have processes underneath, so that friction with the
ground is increased. There is friction between a pencil and notebook.
If there was no friction, writing would be impossible. It is almost
impossible to write with a pencil on very smooth surfaces like glass that
have very little friction.
There are various ways of reducing friciton. If the rubbing surfaces are
smooth or lubricated by grease or water friction between them is reduced. Friciton
can also be reduced by replacing sliding movement into rolling movement. Place several
marbles underneath yours book. Does it move easier?
2
Soles are rough
to prevent
sweeping
31
2.5 A - Let's Move
When we look around, we notice that everything moves. Cars, bicycles, planes are continuously
moving from one place to another. We know that the earth turns around the Sun and the moon turns
around the earth. Briefly, everything in universe moves. Since everything moves in universe, we have to
find a reference point for our own movement.
Scientists call the movement from one place to another or changing one's position
displacement.
Displacement = Final position - Initial position
According to the reference points given on the
left, the displacement of a car moving from
point B to D can be found by:
Displacemet = Final position-Initial position,
Displacement = 6 - 2 = 4 meters.
A B C D E
0 2 4 6 8
Position
Meters
In this example the car that moved from point B to point D had a displacement of 4 meters.
Here, the car's displacement is equal to the distance it covered. But sometimes, this is not the
case.
We know that displacement is the different between the two positions. Displacement is related to
initial position, distance and direction. The sizes that involve the intial point, magnitude and
direction are said to be vectorial.
The distance is the amount of movement made by the car. Distance does not involve any sense of
direction, so it is said to be scalar.
On the diagram given, two different
ways are given to go from home to school.
If the given way is taken:
Green Road
Displacement = 100 meters,
Distance = 100 meters
Displacement is the same in both,
because it means changing positions, However,
the distance covered is different in each case.
If the given way is taken:
Red Road
Displacement = 100 meters,
Distance = 60 + 80 = 140 meters60 meters
80
meters10
0me
ters
Home
School
The first car race took place
in 1909 and the speed of the
fastest car was 105 km/hour
Force and Movement
Did You Know?
32
The difference between velocity and speed is the fact
that:velocity is vectorial , but speed is scalar. In other words, for
finding the velocity of a moving object we use the vectorial
displacement, but for finding its speed we use the scalar value of
distance.
2.5 B - Velocity and Speed
Vectorial Scalar
DISPLACEMENT
VELOCITY =TIME
_____________DISTANCE
SPEED =TIME
_____________
Activity
Straight Road : 200 metreA B
Curving Road : 1500 metre
We can move from point A to point B in 10 seconds when we use the straight road, and in50
seconds when we use the curving road.Then, the velocity and speed for both roads can be
calcualted as:
Velocity = Displacement / Time Velocity = 200 / 10 = 20 m/sec
Speed = Distance / Time Speed = 200 / 10 = 20 m / sec
Straight Road;
Curving Road;
Velocity = Displacement / Time Velocity = 200 / 50 = 4 m/sec
Speed = Distance / Time Speed = 1500 / 50 = 30 m / sec
On a curving road displacement and distance covered are not the same, so velocity and speed
are different.
2
33
TEST - 2
1.
2.
Match each of the following activities with the type of force used in performing that activity.
a)Carrying a table to another place by pulling it.
b)Opening the lid of a jar.
c)Cutting down a tree with an ax.
d)Lifting a weight by using a pulley.
e)Taking off a screw from a piece of wood by using a screwdriver.
f)Turning the pedals of a bicycle.
State the type of force used on each of the following.
Rotational
Force
Linear
Force
3. Look at the dynamometers below, complete the table given and answer the questions.
Object Dynamometer Weight
A
B
C
a)Which object is the heaviest?
b)Which dynamometer must be used
in order to find the weight of an
object of 1 Newton?
4. Which simple machines are found in each of the following objects?
5. According to the references points given above which car is the fastest?
Ferrari Moved from point D to J in 10 seconds
Mercedes Moved from point G to K in 20 seconds.
Honda from point A to E in 50 seconds.Moved
Position
(Meters)
A B C D E F G H I J K
-50 -40 -30 -20 -10 0 10 20 30 40 50
I.
0 N
10 N
20 N
A
II.
0 N
50 N
100 N
B
III.
0 N
1 N
2 N
3 N
C
Force and Movement
34
Add 5 more questions to the
following and make up a survey of 10
questions. Ask these questions to at
least 2 people from your families
and friends.
Q.1 :
_____________________________________
Q.2 :
_____________________________________
Q.3 :
_____________________________________
Q.4 :
_____________________________________
Q.5 :
_____________________________________
What do you think force means?
In everyday life, for which activities do you
use force?
Give 2 examples of activities that use
rotational force?
What type of tools do you use to do work
using less force?
Give examples of simple machines?
Draw the pictures of simple Machines
below in the spaces provided.
�
�
How would we live if
there was no friction?
We can do work using
less force.
Write a composition with a theme that is based
on one of the facts given bove.
____________
_ ____________________
a
___________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
_ ____________________
___________
___________
___________
___________
___________
___________
___________
___________
___________
Write down problems that will need
the use of the formula
below to be solved.
Inclined Plane Pulley
Gear Lever
Wheel and Axle Screw
Work Force Distance= x
Power Work Time= /
Problem:.............................................
:............................................
......................................................
......................................................
Solution
Problem:.............................................
:............................................
......................................................
......................................................
Solution
Multiple Intellegence Activities2
35
Symbolise each simple machine given below with a
different colour and colour the boxes accordingly
Screw Pulley Lever
Inclined Plane Wheel and Axle Gear
State the type of simple machine in each of the
following by using your colour symbols.
b) Scissors
c) Elevator
d) Cart
e) Screwdriver
a) Ax
Write down a brief report on
the negative effects of
speeding in our lives.
--------------------
------------
---------------
-------------------
----------------------
( Title of the report )
( Slogan)
( Information on the subject )
-------------------------- ---------------------------
-------------------------- ---------------------------
--------------------------
---------------------------
--------------------------
--------------------------
--------------------------
--------------------------
Apply the words below to one of your favourite
songs or make up your own song.
--------------------------
--------------------------
--------------------------
--------------------------
--------------------------
--------------------------
--------------------------
--------------------------
There are two types of force
Rotational and Linear .
Select and pick any
simple machine you like.
Screw, inclined plan
Lever, pulley
Do your work using less force
Don't forget the wheel.
State the type of simple machine you used
during each time period given below.
07:00 to 10:00 :
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10:00 to 13:00 :
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13:00 to 15:00 :
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15:00 to 18:00 :
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18:00 to 21:00 :
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Force and Movement
Multiple Intellegence Activities
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