Question

Two drops of the same radius are falling through air with a steady velocity of 5 cm per sec. If the two drops coalesce, the terminal velocity would be (a) 10 cm per sec (b) 2.5 cm per sec (c) 5 × (4)¹/³ cm per sec (d) 5´ √3 cm per sec

Answer 1

Explanation:

If R is radius of bigger drop formed, then

3

4

πR

3

=2×

3

4

πr

3

or R=2

1/3

r

As v

0

∝r

2

∴

v

0

v

01

=

r

2

R

2

=

r

2

(2

1/3

)

2

=2

2/3

or v

01

=v

0

2

2/3

=5(4)

1/3