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 %
D.
4 %
Poisson ratio = 0.5
Since, density is constant therefore change in volume is zero, we have
V = A × l = constant
⇒ log V = log A + log l
∴ Percentage increase in length = 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
Two massless springs of force constants k1 and k2 are joined end to end. The resultant force constant k of the system is
A spring of force constant k is cut into two equal halves. The force constant of each half is
k
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