Question

A small ball (menu) falling under gravity in a viscous medium experiences a drag force proportional to the instantaneous speed u such that $F_{drag}$ = Ku. Then the terminal speed of the ball within the viscous medium is:

• A. $\frac{K}{mg}$
• B. $\frac{mg}{K}$
• C. $\sqrt{\frac{mg}{K}}$
• D. ${\left(\frac{mg}{K}\right)}^2$

Answer 1

Answer: (B)

$\frac{mg}{K}$

For terminal velocity , weight should be balanced by upward force.

Here we have excluded buoyancy force.

Now, $Ku=mg$

$u=\frac{mg}{K}$