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It takes 20 m...

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It takes 20 min to melt 10 g of ice, when rays from the sun are focussed by a lens of diameter 5 cm on a block ofice. If the latent heat for ice is 80 cal/g, the heat received per unit area per unit time at the surface of earth(in cal cm-2 min-1) is(1) 2.04(3) 0.204(2) 3.04(4) 204

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Q. Rays from the sun are focused by a lens of diameter 5 cm on to a block of ice and 10 g of ice is melted in 20 min. Therefore the heat from the sun reaching the earth per min per square centimetre is
(Latent heat of ice

L = 80 c a l g^{- 1}

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Q. The rays of sun are focussed on a piece of ice through a lens of diameter

5

cm, as a result of which

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Q. Select the correct option given below:
Rays from the sun are focused by a lens of diameter

5 c m

on to a block of ice and

10 g

of ice is melted in

20

min.Therefore the heat from the sun reaching the earth per min per square centimetre is (Latent heat of ice L

= 80 c a l g^{- 1}

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Q. The amount of heat needed to melt

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80 c a l / g

(1 c a l = 4.184 J)

Q. A bullet of mass

10 \times 10^{- 3} k g

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(0^{o} c)

990 g

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K . E

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