JEE Main Physics PYQ - Experimental Skills | Important Questions & Solutions

Q 1 :
In the experiment for measurement of viscosity ‘ $η$ ’ of given liquid with a ball having radius R, consider following statements. [2025]

A. Graph between terminal velocity V and R will be a parabola.
B. The terminal velocities of different diameter balls are constant for a given liquid.
C. Measurement of terminal velocity is dependent on the temperature.
D. This experiment can be utilized to assess the density of a given liquid.
E. If balls are dropped with some initial speed, the value of $η$ will change.

Choose the correct answer from the options given below:

B, D and E only
A, C and D only
C, D and E only
A, B and E only

(2)

The terminal velocity of a ball of radius R inside a liquid of viscosity $η$ can be written as $V_{T} = \frac{2 R^{2} g}{η} (σ - ρ),$ where $σ$ is the density of the ball and $ρ$ is the density of the liquid.

Hence,

A is correct since $V_{T} \propto R^{2}$ gives a parabola on a graph.

C is correct since $V_{T} \propto \frac{1}{η}$ and $η$ varies with temperature.

D is correct since $V_{T} \propto (σ - ρ),$ i.e., varies with density of liquid.

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