1.

Let a small block of ice of 0^(@)C fall from a certain height into a water k. It at 0^(@)C, we find that (1)/(8) thof molts when it reaches the ground. The height of the fall is:

Answer»

2100 m
4200 m
100 m
1000 m

Solution :Let m be the mass and h be the height from where it falls.
`therefore` Work done W= mgh.
Heat produced `Q=(W)/(J)=(mgh)/(J)`
Now heat required to MELT `(1)/(8)`th block `Q.=(m)/(8) xxL`
`therefore (mgh)/(J) =(m)/(8)xxL" "RARR h=(JL)/(8_(g))`
`h=(4 CDOT 2xx80xx10^(3))/(8xx10)=4200 m`.
THUS, correct choice is (b).


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