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Give reasons for the following A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.
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Draw a diagram showing the refraction of a light ray from water to glass. Label on it the incident ray, the angle of incidence (/), and the angle of refraction (r)
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A force of 30 N acts on a body and moves it through a distance of 5 m in the direction of force. Calculate the work done by the force.
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A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
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A body, when acted upon by a force of 10 kgf, moves to a distance 0.5 m in the direction of force. Find the work done by the force. Take 1 kgf = 10 N.
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Draw suitable diagrams to illustrate how a beam of light incident parallel to the principal axis is reflected by:
(a) a concave mirror, and (b) a convex mirror
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The diagram (figure) given below shows two parallel rays 1 and 2 incident on (a) a concave mirror, (b) a convex mirror. Draw the reflected rays and mark the focus by the symbol F.

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Electric work done per unit time is ____________.
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The temperature of a substance remains unaffected during its change of state.
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Water at 100°C has more heat than the steam at 100°C.
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Evaporation of a liquid causes cooling.
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Boiling takes place at all temperatures.
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Evaporation takes place over the entire mass of the liquid.
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The process of a gas converting directly into solid is called vaporization.
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At high altitudes, water boils above 100° C.
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Evaporation takes place at ...............temperature.
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.............. process is just reverse of melting.
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