The terminal velocity of a copper ball of radius 5 mm falling through a tank of oil at room temperature is 10 cm s^$$-$$1. If the viscosity of oil at room temperature is 0.9 kg m^$$-$$1 s^$$-$$1, the viscous drag force is :

A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball (v) as a function of time (t) is

If a soap bubble expands, the pressure inside the bubble

Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : The stretching of a spring is determined by the shear modulus of the material of the spring.

Reason (R) : A coil spring of copper has more tensile strength than a steel spring of same dimensions.

In the light of the above statements, choose the most appropriate answer from the options given below: