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 $\left(v\right)$ of the pebble as a function of time $\left(t\right)$

Answer 1

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 Amnswer:$\left(c\right)$