Physics ForcesMr. R Gopie

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Review Questions 1) What is the definition of a force?2) What is the unit of a force?3) What are some types of forces?

Levers

What is a lever?The lever is a simple machine, it consists of a stiff bar which rests on a fulcrum. When you push down at one end the load at the other end is lifted.

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Diagram of a lever

fulcrum

Activity - Levers

You are to be divided into groups of five

Each group is given: a metre rule, masking tape, two cups, marbles and a fulcrum

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Activity - Levers

Each group places twelve marbles at one end (90 cm mark) of the metre rule and label it load

Then place the fulcrum at the 70 cm mark

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Activity - LeversThen each group places the other cup at distances of 10 cm intervals away from the fulcrum, and label it effort

Carefully begin to place marbles into the cup labelled effort

Record the number of marbles in the cup that makes the metre rule lift off and balance

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ResultsDistance from Fulcrum

(cm)Number of Marbles

10

20

30

40

50

60

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What do you observe about the number of marbles and the distance the effort was placed?

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Force Multipliers

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Larger Distance from Effort to Fulcrum

The Output Force is larger than the input force, in other words the lever multiplies the input force by the factor of which the distance between the effort and fulcrum is greater than the distance between the load and fulcrum.

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There is a price to pay for the gain in the force as the load only moves half the distance as the input force

Distance Multipliers

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Distance Multipliers

Distance Multipliers are machines that are designed as distance or speed multipliers, it takes a small movement of the effort and multiplies it to produce a larger movement of the load

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The output force moves further than the input forces-although the size of the force is reduced as a result

What are some examples of levers you have used at

home?The use of a screwdriver to open a tin of paint

The use of a bottle cap opener

The use of a crowbar to move a large boulder

The use a car jack

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Is a Wheelbarrow a lever?

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Types of levers

There are three(3) types of Levers

First Class Levers

Second Class Levers

Third Class levers

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First Class lever

First Class levers have the fulcrum placed between the load and the effort.

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Can you give me an example of a first class lever?

Second Class levers

Second class levers has the load between the fulcrum and the effort.

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Third Class Levers

Third class levers have the effort placed between the load and the fulcrum. The effort always travels a shorter distance and must be greater than the load

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AssessmentGive a definition of a lever?

The lever is a simple machine, it consists of a stiff bar which rests on a fulcrum. When you push down (effort) at one end the load at the other end is lifted.

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Decide which of the following machine is a force multiplier or a distance multiplier?

a) Bottle Cap Opener (Force)

b) Nail Clippers (Force)

c) Door Handle (Distance)

d) Bicycle (Distance)

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3) label the three classes of levers on the diagram

First Class Second Class Third Class

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4) In the following diagrams below label the Fulcrum, load and Effort?

a)

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4) In the following diagrams below label the Fulcrum, load and Effort?

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Any Question?

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Thank You

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