Physics Test 25...

Two radioactive substances A and B have decay constants 5λ and λ, respectively. At t = 0, a sample has the same number of the two nuclei. The time taken for the ratio of the number of nuclei to become (1/e)² will be:

The magnetic field and number of turns of the coil of an electric generator is doubled then the magnetic flux of the coil will:

The frequency f of vibrations of a mass m suspended from a spring of spring consant k is given by f = Cm^xk^y, where C is a dimensionless constant. The values of x and y are, respectively

Three forces are acting on a particle of mass m initially in equilibrium. If the first 2 forces (R₁ and R₂) are perpendicular to each other and suddenly the third force (R₃) is removed, then the acceleration of the particle is

The distance x moved by a body of mass 0.5 kg by a force varies with time t as x = 3t² + 4t + 5 where x is expressed in metre and t in second. What is the work done by the force in the first 2 seconds?

Frequency of a particle executing SHM is 10 Hz. The particle is suspended from a vertical spring. At the highest point of its oscillation the spring is unstretched Maximum speed of the particle is (g = 10 m/s²)

If λ₁ and λ₂  are the wavelengths of the first members of Lyman and Paschen series, respectively, then λ₁ : λ₂ is:

Three rods of Copper, Brass and Steel are welded together to from a Y –shaped structure. Area of cross – section of each rod = 4 cm². End of copper rod is maintained at 100°C where as ends of brass and steel are kept at 0°C. Lengths of the copper, brass and steel rods are 46, 13 and 12 cms respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are 0.92, 0.26 and 0.12 CGS units respectively. Rate of heat flow through copper rod is

In an experiment for determination of refractive index of glass of a prism by i – δ plot, it was found that a ray incident at an angle of 35° suffers a deviation of 40° and that it emerges at an angle of 79°. In that case, which of the following is closest to the maximum possible value of the refractive index?

In an electron microscope, the resolution that can be achieved is of the order of the wavelength of electrons used. To resolve a width of 7.5 × 10^-12 m, the minimum electron energy required is close to: