Q. 1

# 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 Fig. 10.1, indicate the one that represents the velocity (v) of the pebble as a function of time (t).

A.

B.

C.

D.

Fig. 10.1

Answer :

When a pebble is dropped in a fluid, a variable force called viscous force acts on it. This force increases the velocity of the pebble until it becomes constant. This constant velocity is called the critical velocity. Since, the force is variable, acceleration is variable and so v-t graph is curved and not a straight line to which critical velocity v_{c} is an asymptote.

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