11.

The Poisson's ratio of a material is 0.5. If a force is applied to a wire of this material, there is a decrease in the cross-sectional area by 4%. The percentage increase in the length is

• 1 %

• 2 %

• 2.5 %

• 4 %

Two spheres of equal masses but radii r₁ and r₂ are allowed to fall in a liquid of infinite column. The ratio of their terminal velocities is

• 1

• r₁ : r₂

• r₂ : r₁

• $\sqrt{{\mathrm{r}}_1} : \sqrt{{\mathrm{r}}_2}$

Two massless springs of force constants k₁ and k₂ are joined end to end. The resultant force constant k of the system is

• $\mathrm{k} = \frac{{\mathrm{k}}_1 + {\mathrm{k}}_2}{{\mathrm{k}}_1{\mathrm{k}}_2}$

• $\mathrm{k} = \frac{{\mathrm{k}}_1 - {\mathrm{k}}_2}{{\mathrm{k}}_1{\mathrm{k}}_2}$

• $\mathrm{k} = \frac{{\mathrm{k}}_1{\mathrm{k}}_2}{{\mathrm{k}}_1 + {\mathrm{k}}_2}$

• $\mathrm{k} = \frac{{\mathrm{k}}_1{\mathrm{k}}_2}{{\mathrm{k}}_1 - {\mathrm{k}}_2}$

A spring of force constant k is cut into two equal halves.  The force constant of each half is

• $\frac{\mathrm{k}}{\sqrt{2}}$

• k

• $\frac{\mathrm{k}}{2}$

• 2k

Two rods of equal length and diameter have thermal conductivities 3 and 4 units respectively. If they are joined in series, the thermal conductivity of the combination would be

• 3.43

• 3.5

• 3.4

• 3.34

19 g of water at 30°C and 5 g of ice at -20°C are mixed together in a calorimeter. What is the final temperature of the mixture ? (Given specific heat of ice = 0.5 cal g^-1 (C)^-1 and latent heat of fusion of ice = 80 cal g^-1)

• 0°C

• − 5°C

• 5°C

• 10°C

It is difficult to cook rice in an open vessel by boiling it at high altitudes because of

• low boiling point and high pressure

• high boiling point and low pressure

• low boiling point and low pressure

• high boiling point and high pressure

The height of a waterfall is 50 m. If g = 9.8 ms^-2 the difference between the temperature at the top and the bottom of the waterfall is

• 1.17°C

• 2.17°C

• 0.117°C

• 1.43°C

The equation of state for n moles of an ideal gas is pV = nRT, where R is a constant. The SI unit for R is

• Jk^-1 per molecule

• JK^-1 mol^-1

• JKg^-1K^-1

• Jk^-1g^-1

One kg of copper is drawn into a wire of 1 mm diameter and a wire of 2 mm diameter. The resistance of the two wires will be in the ratio

• 2 : 1

• 1 : 2

• 16 : 1

• 4 : 1