Question

A tall cylinder is filled with viscous oil. A round pebble is dropped from the top with zero initial velocity. From the plot shown in figure, indicate the one that represents the velocity $v$ of the pebble as a function of time $t$

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

When a round pebble is dropped from the top of a tall cylinder, filled with viscous oil, viscous force $(F=6\pi \eta rv)$ i.e. a variable force will act which increases with increase in speed.

At the equilibrium, pebble will attain constant velocity known as terminal velocity. As the force is variable, hence acceleration is also variable, so $v-t$ graph will not be a straight line. First velocity increases and then becomes constant known as terminal velocity.


Final Answer: (c)