21.

The apparent frequency in Doppler's effect does not depend upon:

• speed of the observer

• distance between observer and source

• speed of the source

• frequency from the source

Two simple pendulums whose lengths are 100 cm and 121 cm are suspended side by side. Their bobs are pulled together and then released. After how many minimum oscillations of the longer pendulum, will the two be in phase

• 11

• 10

• 21

• 20

A body executing SHM has its velocity 10 cm/s and 7 cm/s when its displacements from the mean position are 3 cm and 4 cm respectively. The length of the path is :

• 10 cm

• 9.5 cm

• 4 cm

• 11.36 cm

A 700 g solid cube having an edge of length 10 cm floats in water. The volume of the cube outside water is :

• 2.4 cm³

• 4.8 cm³

• 300 cm³

• 500 cm³

A one-metre long steel wire of cross-sectional area 1mm² is extended by 1 mm. If Y=2 x 10¹¹ N/m², then the work done is :

• 0.1 J

• 0.2 J

• 0.3 J

• 0.4 J

A light source approaches the observer with a velocity of 0.5 c. Doppler's shift for a light of wavelength 5500 Å is:

• 616 Å

• 1833 Å

• 5500 Å

• 6160 Å

At 27°C, a motor car tyre has a pressure of 2 atmospheres. The temperature at which the tyre suddenly burst will be : (Given: γ_air = 1.4)

• 246.1 K

• 250 K

• 246 K

• 248 K

Consider the following equation of Bernoulli's theorem

$\mathrm{P} + \frac{1}{2}{\mathrm{\rho v}}^2 + \mathrm{\rho gh} = \mathrm{K}$ (constant)

The dimensions of K/P are same as that of which of the following?

• Thrust

• Pressure

• Angle

• Viscosity

Why the dam of the water reservoir is thick at the bottom?

• Quantity of water increases with depth

• Density of water increases with depth

• Pressure of water increases with depth

• Temperature of water increases with depth

A beaker is completely filled with water at 4°C. It will overflow if:

• heated above 4°C

• cooled below 4°C

• both heated and cooled above and below 4°C respectively

• none of these