A conducting sphere of radius 1O cm is charged with 10 μC. Another uncharged sphere of radius 20 cm is allowed to touch it for some time. After that if the spheres are separated, then surface density of charges on the spheres will be in the ratio of
1 : 4
1 : 2
1 : 3
1 : 1
B.
1 : 2
Radius of conducting sphere (R1) = 10 cm
charge on the conducting sphere = 10 μC
Radius of uncharged sphere (R2) = 20 cm
For a spherical conductor, the density of charge is proportional to its radius. Therefore ratio of the density of charges of the spheres will be 1 : 2.
If vο be the orbital velocity of satellite in a circular orbit close to the earth's surface and ve is the escape velocity from the earth, then relation between the two is
vο = ve
ve =
ve = vο
ve = 2 vο
Assertion: Planet is a heavenly body revolving round the sun.
Reason: Star is luminous body made of gaseous material.
If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If the assertion is true but the reason is false.
If both assertion and reason are false.
Assertion: It is difficult to move a cycle along the road with its brakes on.
Reason: Sliding friction is greater than rolling friction.
If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If the assertion is true but the reason is false.
If both assertion and reason are false.
Assertion: In an elastic collision of two billiard balls, the total kinetic energy is conserved during the short time of oscillation of the balls (i.e. when they are in contact).
Reason: Energy spent against friction does not follow the law of conservation of energy.
If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If the assertion is true but the reason is false.
If both assertion and reason are false.
A siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s. Frequency of the sound to be heard by the listener is (Take velocity of sound as 300 m/s)
733.3 Hz
481.2 Hz
644.8 Hz
286.5 Hz
A string in a musical instrument is 50 cm long and its fundamental frequency is 800 Hz. If a frequency of 1000 Hz is to be produced, then required length of string is
62.5 cm
40 cm
50 cm
37.5 cm
If equation of dound wave is y = 0.0015 sin ( 62.8 x + 316 t ) then its wavelength will be
0.2 unit
0.3 unit
0.1 unit
2 unit