◄UNIT 1: Mechanical and blacksmith toolsUNIT 3:Objects production►

UNIT 2:Simple machines

  • UNIT 2:Simple machines

    1. Look at the picture below showing people working in a construction

    site.

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    2. Is it easier to move materials as shown in the picture?
    3. Suggest what you can use to move the materials shown in the picture faster.
    2.1 Definition of simple machine
    Find out
    1. What a simple machine is.
    2. The difference between working with and without a simple

    machine.

    Activity 2.1 Carrying heavy weight
    1. Look at the following pictures.
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    2. Which one above finds it easier to carry the load? Explain why?

    Simple machines are simple devices that make work easier. Examples

    include wheelbarrow, hammer, screwdriver, spade among others.

    2.2 Types of simple machines
    Find out

    How different simple machines are used to do work.

    Activity 2.2 Identifying simple machines

    1. Look at the following pictures5

    2. Name the types of simple machines shown above.

    Simple machines are of different types. The various categories of
    simple machines are:
    • Levers e.g wheelbarrow,crow bar
    • Wheel and axle e.g windlass
    • Pulleys e.g elevator, cargo lift
    • Inclined planes e.g ladder
    • Wedges e.g metallic saw

    • Screws e.g screwdriver

    a) Levers
    Activity 2.3       Uses of simple machines
    1. Discuss how each group of levers is used. Write a report and

    present the report to the rest of the class.

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    Activity 2.4      Practicing the use of levers

    1. Practice playing on a see-saw as shown below with a friend.

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    a) Why did you go down and your friend up?
    b) Change positions along the wooden plank. What happens?

    2. Now, try moving a stone using a crowbar as shown below.

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    Were you able to move the stone? Now try moving the stone
    without the crowbar? Was it easier? Why?
    3. Which point on the see-saw is:
    a) Effort?
    b) Load?
    c) Pivot or fulcrum?
    How about on the crowbar?

    4. What does your findings tell you about levers?

    Definition
    A lever is a stiff bar with a fixed turning point called a fulcrum or pivot.

    A lever was one of the first simple machines to be discovered in life.

    Parts of the lever
    A lever is made up of effort, fulcrum and load. These parts are shown in

    the diagram below.

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    Depending on the position of these parts, levers are put into different

    categories.

    Classes of levers
    Activity 2.5     Identifying classes of levers based on
                            the position of the effort, fulcrum or load
    1. Do the following:

    a) Try removing a piece of nail from wood as shown below.

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    b) Open a bottle of soda using a bottle opener as shown below.

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    c) Scoop sand using a spade as shown below.

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    Study questions
    In the three cases above,
    i) Where did you apply energy to lift the load?
    ii) Where was the turning point?
    iii) What was the position of the load?
    2. Draw a diagram to show the parts of the lever in the positions
    above.
    3. Find out more about the types of levers based on the positions
    of the three parts above. Come up with a table on classes of

    levers as shown below.

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    • The turning point of a lever is called pivot or (fulcrum).
    • The force applied to the lever is called effort.
    • The resistance against which the force is applied is called load.
    Levers are put into three classes depending on the position of the fulcrum,
    effort or load.
    i) First class levers
    In first class levers, the fulcrum is between the load and the effort.

    The pictures below are examples of first class levers.

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    Work to do
    Find out other machines which belong to this category. Write the list
    down in your notebook.

    ii) Second class levers

    In this class of levers, the load is between the effort and the fulcrum.

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    Examples of levers in this class include paper cutter, nut-cracker,

    wheelbarrow and bottle opener in use.

    Work to do
    Find out other machines which belong to this category. Write down
    the list in your notebook.

    iii) Third-class levers
    In this class, the effort is between the load and the fulcrum.

    The pictures below are examples of third-class levers.

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    Examples of levers in this class include a tennis racket, fishing rod, baseball

    bat, the human arm, a broom, tweezers and a spade in use.

    Work to do
    Find out other machines which belong to this category. Write down

    the list in your notebook.

    b) Wheel and axle
    • The wheel and axle is a simple machine that has two wheels,
    one large and smaller one fixed together. Examples include a door

    handle, a steering wheel and a windlass.

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    c) Pulleys
    • Pulleys - a pulley is a wheel that rotates around an axle which has
    a groove where a rope or a string fits.
    • Types of pulleys include: A single fixed pulley, movable pulley

    and the block and tackle pulley system.

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    d) Inclined plane
    • Inclined plane - this is any device with a sloping surface. Examples
    of inclined planes are: staircase, a ladder, a meandering road on a

    steep hill, a ramp among others.

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    e) Wedges
    • Wedges - a wedge is an object with one sharp cutting edge.

    Examples of wedges are knife, razorblade, axe and chisel.

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    f) Screw
    • Screws – A screw is a metal rod with a raised thread running
    round it.
    • Screws are used to hold and join pieces of metals or wood together.

    • Screws are also used in jacks to raise heavy objects like cars.

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    2.3 Dangers when using simple machines
    Find out

    The dangers of using simple machines.

    Activity 2.6 Dangers when using simple machines
    1. Which dangers do you face when using simple machines? Discuss
    in groups and write a report. Choose one group member to
    present the report in class

    Some dangers that we face when using simple machines include:

    • We can get pricked by pointed parts of the machines.

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    • Machines with sharp edges can cut our skin.

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    • We can fall when using inclined planes such as ladder
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    • We can get hurt while using machines like bicycle.

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    Remember!
    We should always buy quality machines and tools. Cheap tools or
    machines may cause accidents. They may also get spoils quickly , this

    makes it expensive in the long run.

    2.4 Safety in using simple machines
    Find out
    How to use simple machine safely without any danger?
    Activity 2.7     Identifying protective methods when using
                            simple machines
    1. How can we avoid the dangers associated with the use of simple
    machine?
    2. Discuss in your group and write short notes.

    3. Compare your report with that of other classmates.

    • We should always be careful when using simple machines to avoid
    accidents.
    • We should always wear protective clothing when using simple
    machines.
    • Protective clothing include overalls, goggles, gumboots, gloves,

    mouth and nose masks among others.

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    Self –Test 2.1
    1. What is a lever?
    2. Look at the diagram below. Can you label the parts named X,Y

    and Z?

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    3. How would you know whether a given machine is:
    a) First class lever?      b) Second class lever?
    c) Third class lever?

    4. A ladder is an example of ___________. (lever, inclined plane)

                              UNIT TEST 2
    1. What is the importance of the invention of simple machines by
    early human beings?
    2. Where do we apply simple machines in our daily lives.
    3. Give three examples of simple machines where wheel and axle is
    applied.
    4. In which category of simple machines does the one shown below

    belong to?

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    5. Given the following list of simple machines: wheelbarrow, nut
    cracker, tweezers, tong, pliers and a pair of scissors. Put them

    into three groups as shown in the following table.

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    6. Name parts of your body that act as levers.
    7. Go for a tour around your school. Observe how the roads are
    constructed on steep slopes. Why do you think the roads are
    constructed like that?
    8. What is the use of screws and bolts? What type of simple machines
    are they?
    9. How would you advise primary 6 pupils using simple machines
    with sharp edges?
    10. The diagram below shows a claw hammer being used to

    remove a nail from a piece of wood.

    a

    Based on the diagram, the hammer is _________ class of lever.
    11. Write true or false:
    a) A simple machine uses a single applied force to do work
    against a single load. _________
    b) A simple machine enables people to do work with less effort
    and at greater speed. ____________
    c) Life became very safe when early human beings discovered
    the use of simple machines. _________
    d) The force applied on a simple machine is always greater
    than the work done. _____________
    e) Most levers are examples of simple machines.

    12. Which type of simple machine is shown below?

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    A. Lever                  B. Wedge
    C. Screw                 D. Single fixed pulley
    13. Mugabo sweeps the class floor every morning using a broom as

    shown below. To which class of lever is the broom?

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    A. Fist class Lever
    B. Third class Lever
    C. Second class Lever
    14. What is a simple machine and how does it help to make work
    easier?
    15. Visit a construction site and list the simple machines used there.

    16. Why do roads on a steep slope meander as shown below?

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    17. What is a lever? _____________________
    18. Look at the diagram below. Can you label the parts named X,Y

    and Z?

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    19. A ladder is an example of ___________ (lever, inclined plane)

    ◄UNIT 1: Mechanical and blacksmith toolsUNIT 3:Objects production►