1.

Eight equal drops of water are falling through air with a steady velocity of 10 cms^(-1).If the drops combine to form a single drop big in size,then the terminal velocity of this big drop is

Answer»

20 cm/s
30 cm/s
40 cm/s
60 cm/s

Solution :Here volume remains the same.
`therefore4/3piR^(3)=8 4/3pir^(3)`
`rArrR=2r`
Since TERMINAL velocity, v`=2/(9eta).r^(2)[p-sigma]g`
`rArrvpropr^(2)`
`therefore` terminal velocity becomes 4 times as RADIUS becomes DOUBLE.
`therefore` New terminal velocity `= 4 xx 10` = 40 emfs.
Thus the CORRECT choice is (c).


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