Level 2

A thin wire is bent in the form of a ring of diameter $3.0 \mathrm{cm}$. The ring is placed horizontally on the surface of soap solution and then raised up slowly. Upward force necessary to break the film formed between the ring and the solution is -

In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius $2.0\times {10}^{-5} \mathrm{m}$ and density $1.2\times {10}^3 \mathrm{kg} {\mathrm{m}}^{-3}$? Take viscosity of liquid $=1.8\times {10}^{-5} \mathrm{N} \mathrm{s} {\mathrm{m}}^{-2}.$ (Neglect buoyancy due to air).

Two rain drops falling through air have radii in the ratio$1: 2$. They will have terminal velocity in the ratio________

The temperature of equal masses of three different liquids $x, y$ and $z$ are $10°\mathrm{C}, 20°\mathrm{C}$ and $30°\mathrm{C}$ respectively. The temperature of mixture when $x$ is mixed with $y$ is $16°\mathrm{C}$ and that when $y$ is mixed with $z$ is $26°\mathrm{C}$. The temperature of mixture when $x$ and $z$ are mixed will be :

A cube, a cylinder (of height equal to its diameter) and a sphere, all solid, are made of metal and are of identical mass. If all the three shapes having initial temperature $50 °\mathrm{C}$ are put in a large reservoir of water at $10 °\mathrm{C}.$ Which of the above three shapes cools the fastest?

Let there be four identical cubes having colours blue, red, black and white. When they are heated together and allowed to cool under identical conditions, which cube will cool at the earliest?

The excess pressure inside an air bubble of radius $r$ just below (inside) the surface of the water is ​$P_1$. The pressure inside a drop of the same size (radius) which is just outside the water surface is $P_2$. If $T$ is the surface tension then

A bucketful of water is kept in a room and it cools from ${75}^{\circ }\mathrm{C}$ to ${70}^{\circ }\mathrm{C}$ in ${\mathrm{T}}_1 \min$, from ${70}^{\circ }\mathrm{C}$ to ${65}^{\circ }\mathrm{C}$ in ${\mathrm{T}}_2 \min$, and from ${65}^{\circ }\mathrm{C}$ to ${60}^{\circ }\mathrm{C}$ in ${\mathrm{T}}_3 \min$. Then