21.

Two bars A and B of circular cross-section and same volume made of same material are subjected under same tension. If the diameter of A is half that of B. The ratio of extension of A to B will be

• 16

• 2

• $\frac{1}{4}$

• 4

Water rises in a capillary upto a extension height such that upward force of surface tension balances the force of 75 x 10^-4 N due to weight of water. If surface tension of water is 6x10^-2 N/m.The internal circumference of the capillary must be

• 12.5$\times {10}^{-2}$m

• 6.5$\times {10}^{-2}$m

• 0.50$\times {10}^{-2}$m

• 1.25$\times {10}^{-2}$m

A capillary tube of radius r can support a liquid of weight 6.28 x 10^-4 N. If the surface tension of the liquid is 5 x 10^-2N/m. The radius of capillary must be

• $2.0\times {10}^{-3}\mathrm{m}$

• $2.0\times {10}^{-4}$m

• 1.5$\times {10}^{-3}\mathrm{m}$

• $12.5\times {10}^{-4}\mathrm{m}$

The soap bubbles have radii in the ratio 2: 1 ratio of excess pressure in side there is

• 1:4

• 4:1

• 2:1

• 1:2

Standing wave are produced in a 10 m long stretched string. If the string vibrates in 5 segments and the wave velocity is 20 m/s. The frequency is

• 10Hz

• 5Hz

• 4Hz

• 2Hz

A steel wire 0.5 m long has a total mass 0.01 kg and stretched with a tension of 800 N. The frequency with which it vibrates in its fundamental note will be

• 4Hz

• 2Hz

• 200Hz

• 160Hz

 A cord attached to a vibrating tuning fork is divided into six segments under tension of 36 N. It will be divided into four segments, if the tension is

• 48N

• 81N

• 24N

• 16N

The equation of travelling wave is y= 60 cos (1800 t-6x) where y is in micron and t in second and x in metre. The ratio of maximum particle velocity to velocity of wave propagation is

• 3.6

• 3.6$\times {10}^{-4}$

• $3.6\times {10}^{-11}$

• $3.6\times {10}^{-6}$

In a sinusoidal wave, the time required for a particular point to move from maximum displacement to zero displacement is 0.170.The frequency of the wave will be

• 2.94Hz

• 0.73Hz

• 0.36Hz

• 1.47Hz

 The root mean square velocity of hydrogen molecules of an ideal hydrogen gas kept in a gas chamber at 0C is 3180 m/s. Calculate the pressure of hydrogen gas:$\left(\mathrm{Density} \mathrm{of} \mathrm{hydrogen} \mathrm{gas}=8.99\times {10}^{-2}\raisebox{1ex}{$\mathrm{kg}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{m}}^3$}\right., \mathrm{atmosphere}= 1.01\times {10}^5\raisebox{1ex}{$\mathrm{N}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{m}}^2$}\right.\right)$

• 3.0atm

• 2.0atm

• 1.5atm

• 1.0atm