For a sphere falling in the constant drag co-efficient regime, its terminal velo

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Question
For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
Options
A. d
B. d
C. d²
D. 1/d

Correct Answer

d²

Mechanical Operations problems

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2. The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
Options
A. Reynold's
B. Froude
C. both (a) & (b)
D. neither (a) nor (b)

3. At low Reynold's number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
P_o = ?/?N³ D⁵ : Power number
Re = ? N D²/?: Reynold's number
N is the impeller rotational speed, and D is the impeller diameter.
Options
A. P_o ? Re^-1.0
B. P_o ? Re^0.0
C. P_o ? Re^0.5
D. P_o ? Re^1.0

9. For efficient grinding, ball mills must be operated
Options
A. at a speed less than the critical speed.
B. at a speed more than the critical speed.
C. at a speed equal to the critical speed.
D. with minimum possible small balls.

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