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Why is it that the birds flying in the sky do not cast their shadow on the earth?
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Tick the correct answer.
Umbra is a region of
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Answer the following.
How is a shadow formed? Write the conditions required for a shadow to form.
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In a machine, an effort of 10 kgf is applied to lift a load of 100 kgf. What is its mechanical advantage?
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The mechanical advantage of a machine is 5. How much load it can exert for the effort of 2 kgf?
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The mechanical advantage of a machine is 2. It is used to raise a load of 15 kgf. What effort is needed?
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Solve the following numerical problem.
The length of a lever is 2 m. Calculate its mechanical advantage if the fulcrum is situated at a distance of 40 cm from the effort.
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Solve the following numerical problem.
Calculate the mechanical advantage of a crowbar of length 240 cm if its fulcrum is situated at a distance of 40 cm from the load.
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Write true or false.
Every measurement involves two things – a number and a unit.
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What are the S.I. units of
- mass
- length
- time and
- temperature.
Write their names and symbols.
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Match the following.
| Column A | Column B |
| (1) Length | a. kilogram |
| (2) Mass | b. cubic metre |
| (3) Area | c. metre |
| (4) Volume | d. square metre |
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Fill in the blank.
In the ............ system, length is measured in centimetres.
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Fill in the blank.
The darkest portion of a shadow is called the ................
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Fill in the blank.
The less dark portion of a shadow is called the .................
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Select the correct alternative.
Umbra is a region of
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Select the correct alternative.
Penumbra is a region of
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What is a shadow? Give a reason for its formation.
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Draw a ray diagram to show the formation of the shadow of an opaque object by a point source of light. How is the size of shadow affected if the screen is moved away from the object?
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State two differences between an umbra and a penumbra.
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Draw a ray diagram to show the formation of umbra alone.
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