At which of the following temperatures, the value of surface tension of water is minimum
4º C
25º C
50º C
75º C
Work done in splitting a drop of water of 1 mm radius into 64 droplets is (surface tension of water = 72x 10-3 J/m2)
2.0 x 10-6 J
2.7 x 10-6 J
4 x 10-6 J
5.4 x 10-6 J
B.
2.7 x 10-6 J
Hence, work done
W = T × (64 × 4πr2 - 4πR2 )
W = 2.7 × 10-6 J
A black body at 227°C radiates heat at the rate of 7 cal/cm2 -s. At a temperature of 727°C. the rate of heat radiated in the same units will be
80
60
50
112
The vertical extension in a light spring by a weight of 1 kg suspended from the wire is 9.8 cm. The period of oscillation is
20π s
2π s
200 s
A particle of mass 10 g is describing SHM along a straight line with a period of 2 s and amplitude of 10 cm. Its kinetic energy when it is at 5 cm from its equilibrium position is
3.75 π2 erg
375 π2 erg
0.375 π2 erg
37.5 π2 erg
The angular amplitude of a simple pendulum is θ0 The maximum tension in its string will be
mg(1 - θ0)
mg(1 + θ0)
mg(1 - )
mg(1 + )
It is possible to recognize a person by hearing his voice even if he is hidden behind a solid wall. This is due to the fact that his voice
has a definite capacity
has a definite quality
has definite pitch
can penetrate the wall
The velocity of sound in air at NTP is 330 m/s. What will be its value when the temperature is doubled and pressure is halved?
330 m/s
165 m/s
330 m/s
Two gases A and B at same pressure contain a number of moles n1 and n2. Their volume temperature graphs are shown in the figure. Then the ratio n1/n2
1
1/2
1/3
3
A source of sound emits 200 W power which is uniformly distributed over a sphere of 10 m radius. What is the loudness of sound on the surface of a sphere?
200 dB
200π dB
120 dB
120π dB