List of top Physics Questions

The temperature at which the rms speed of oxygen molecules is 75\% of the rms speed of nitrogen molecules at a temperature of \( 287^\circ C \) is: 

A big liquid drop splits into 'n' similar small drops under isothermal conditions, then in this process:

A body of mass 'm' tied to one end of a string is whirled in a vertical circle of radius 'R' with zero tension in the string at its highest point. The angle made by the string with the vertical when the kinetic energy of the body becomes half of its maximum kinetic energy is:
The thickness of a uniform rectangular metal plate is 5 mm and the area of each surface is 3750 cm\(^2\). In steady state, the temperature difference between the two surfaces of the plate is 14°C. If the heat flowing through the plate in one second from one surface to the other surface is 42 J, then the thermal conductivity of the metal is:
Match List I with List II.
List I
(Spectral Lines of Hydrogen for transitions from)		List II
(Wavelength (nm))
A.n2 = 3 to n1 = 2I.410.2
B.n2 = 4 to n1 = 2II.434.1
C.n2 = 5 to n1 = 2III.656.3
D.n2 = 6 to n1 = 2IV.486.1
Choose the correct answer from the options given below:
The speed of a transverse wave in a stretched string 'A' is 'v'. Another string 'B' of same length and same radius is subjected to same tension. If the density of the material of the string 'B' is 2\% more than that of 'A', then the speed of the transverse wave in string 'B' is
The density of a substance of mass 5.318 g which occupies a volume of 2.43 cm³ is (up to correct significant figures):
An element consists of a mixture of three isotopes A, B, and C of masses \( m_1 \), \( m_2 \), and \( m_3 \) respectively. If the relative abundances of the three isotopes A, B, and C is in the ratio 2:3:5, the average mass of the element is:
Two spherical rain drops of radii in the ratio 4:5 are falling vertically through air. The ratio of the terminal velocities of the rain drops is:
The concentration of electrons in an intrinsic semiconductor is \( 6 \times 10^{15} \, m^{-3} \). On doping with an impurity, the electron concentration increases to \( 4 \times 10^{22} \, m^{-3} \). In thermal equilibrium, the concentration of the holes in the doped semiconductor is:
A cannon fires two similar shells one after the other each with a velocity of 100 m/s at angles 60$^\circ$ and 30$^\circ$ respectively with the horizontal such that they both hit the target at the same time. The time interval between the firing of the two shells is (Acceleration due to gravity = 10 m/s²).
An arc making an angle \(15^\circ\) at the center is removed from a ring of mass \( M \) and radius \( R \). The moment of inertia of the remaining ring about an axis passing through its center and perpendicular to its plane is:
At room temperature, gaseous hydrogen is bombarded with a beam of electrons of 13.6 eV energy. The series to which the emitted spectral line belongs to:
The efficiency of a reversible heat engine working between two temperatures is 50\%. The coefficient of performance of a refrigerator working between the same two temperatures but in reverse direction is:
The half-life of a radioactive substance is 12 minutes. The time gap between 28\% decay and 82\% decay of the radioactive substance is:
A liquid drop of diameter 2 mm breaks into 125 identical drops, then the change in the surface energy is:
If a ray of light passes through an equilateral prism such that the angle of incidence and the angle of emergence are both equal to 70\% of the angle of the prism, then the angle of minimum deviation is:
A supposition without assuming that it is true is:
A cannon fires two similar shells one after the other each with a velocity of 100 m/s at angles 60$^\circ$ and 30$^\circ$ respectively with the horizontal such that they both hit the target at the same time. The time interval between the firing of the two shells is (Acceleration due to gravity = 10 m/s²).
Two solid spheres of radii \( r_1 \) and \( r_2 \) (\( r_2>r_1 \)) made of the same material are kept in contact. The distance of their center of mass from their point of contact is:
If the tension applied to a string is decreased by 36\%, then the fundamental frequency of the transverse waves of the string is:
A liquid drop of diameter 2 mm breaks into 125 identical drops, then the change in the surface energy is:
Two identical balls having like charges placed at a certain distance apart, repel each other with a force \( F \). When they are brought in contact and then moved apart to a distance equal to half of their initial separation, the force of repulsion between them becomes \( 4.5F \). The ratio of the initial charges of the balls is:
The work done in blowing a soap bubble of volume \( V \) is \( W \). The work done in blowing the bubble of volume \( 2V \) from the same soap solution is?
A block kept on a frictionless horizontal surface is connected to one end of a horizontal spring of constant \( 100 \, \text{Nm}^{-1} \), whose other end is fixed to a rigid vertical wall. Initially, the block is at its equilibrium position. The block is pulled to a distance of \( 8 \) cm and released. The kinetic energy of the block when it is at a distance of \( 3 \) cm from the mean position is?