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State one advantage of single movable pulley.
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The diagram below shows two parallel rays A (Orange) & B (Blue) incident from air, on air-glass boundary.

- Copy and complete the path of the rays A and B.
- How do the speeds of these rays differ in glass?
- Are the two refracted rays in glass parallel? Give a reason.
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A radioactive element is placed in an evacuated chamber. Then the rate of radioactive decay will ______.
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| Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load. |
Why should she connect more number of pulleys in the upper fixed block?
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Complete the following radioactive reaction:
\[\ce{^-_-X -> ^-_-Y + ^4_2He -> ^234_91Z + ^0_-1e}\]
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In the following atoms, which one is a radioisotope? Give one use of this isotope.
O16, C14, N14, He4
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A block and tackle system of pulleys has a velocity ratio of 4.
- Draw a labelled diagram of the system indicating clearly the direction of the load and effort.
- Calculate the potential energy of the load 100 kgf lifted by this pulley to a height 5 m. (g = 10 ms−2)
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Name the type of single pulley that has an ideal mechanical advantage equal to 2. Draw a labelled diagram of the pulley mentioned by you.
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Which colour of white light travels fastest in any medium except air?
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A ray of light strikes the surface of a rectangular glass slab such that the angle of incidence in air is
- 0°,
- 45°.
In each case, draw a diagram to show the path taken by the ray as it passes through the glass slab and emerges from it.
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Where can a body execute natural vibrations?
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Why is the switch put in the live wire?
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What precaution do you take while handling a switch?
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Name the wire to which a switch is connected.
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Define kilowatt hour.
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What is lateral displacement?
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Why does sun appear red at sunrise and sunset?
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Give one example of damped vibrations
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Draw the diagram of a dual control switch when the appliance is switched ‘ON’.
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Which color of white light is scattered the least and why?
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