Eight spherical rain drops of the same mass and radius are fallin… - Vidyadip

MCQ

Eight spherical rain drops of the same mass and radius are falling down with a terminal speed of $6\, cm -s^{-1}$ . If they coalesce to form one big drop, what will be the terminal speed of the bigger drop ? (Neglect the buoyancy of the air) ....... $cm -s^{-1}$

A
$1.5$
B
$6$
✓
$24$
D
$32$

✓

Answer

Correct option: C.

$24$

c
$\mathrm{R}=\mathrm{n}^{1 / 3} \mathrm{r}=8^{1 / 3} \mathrm{r}=2 \mathrm{r}$

$\frac{V_{T_{1}}}{V_{T_{2}}}=\left(\frac{R_{1}}{R_{2}}\right)^{2}$

$\mathrm{V}_{\mathrm{T}_{2}}=6 \times 4$

$\mathrm{V}_{\mathrm{T}_{2}}=24 \mathrm{cm} / \mathrm{s}$

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