PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Physics

If the speed of a rod moving at a relativistic speed parallel to its length is doubled,

(a) the length will become half of the original value
(b) the mass will become double of the original value
(c) the length will decrease
(d) the mass will increase

Which of the following quantities related to an electron has a finite upper limit?

A rod of rest length L moves at a relativistic speed. Let L' = L/γ. Its length

(a) must be equal to L'
(b) may be equal to L
(c) may be more than L' but less than L
(d) may be more than L

When a rod moves at a relativistic speed v, its mass ________________ .

Consider an excited hydrogen atom in state n moving with a velocity υ(ν<<c). It emits a photon in the direction of its motion and changes its state to a lower state m. Apply momentum and energy conservation principles to calculate the frequency ν of the emitted radiation. Compare this with the frequency ν₀ emitted if the atom were at rest.

By what fraction does the mass of a spring change when it is compressed by 1 cm? The mass of the spring is 200 g at its natural length and the spring constant is 500 N m⁻¹.

Find the increase in mass when 1 kg of water is heated from 0°C to 100°C. Specific heat capacity of water = 4200 J kg⁻¹ K⁻¹.

Find the loss in the mass of 1 mole of an ideal monatomic gas kept in a rigid container as it cools down by 100°C. The gas constant R = 8.3 J K⁻¹ mol⁻¹.

By what fraction does the mass of a boy increase when he starts running at a speed of 12 km h⁻¹?

A 100 W bulb together with its power supply is suspended from a sensitive balance. Find the change in the mass recorded after the bulb remains on for 1 year.

The energy from the sun reaches just outside the earth's atmosphere at a rate of 1400 W m⁻². The distance between the sun and the earth is 1.5 × 10¹¹ m.
(a) Calculate the rate  which the sun is losing its mass.
(b) How long will the sun last assuming a constant decay at this rate? The present mass of the sun is 2 × 10³⁰ kg.

An electron and a positron moving at small speeds collide and annihilate each other. Find the energy of the resulting gamma photon.

Find the mass, the kinetic energy and the momentum of an electron moving at 0.8c.

Through what potential difference should an electron be accelerated to give it a speed of (a) 0.6c, (b) 0.9c and (c) 0.99c?

Find the speed of an electron with kinetic energy (a) 1 eV, (b) 10 keV and (c) 10 MeV.

What is the kinetic energy of an electron in electron volts with mass equal to double its rest mass?

Find the speed at which the kinetic energy of a particle will differ by 1% from its nonrelativistic value \[\frac{1}{2} m_o v^2 .\]

A point source emitting alpha particles is placed at a distance of 1 m from a counter which records any alpha particle falling on its 1 cm² window. If the source contains 6.0 × 10¹⁶ active nuclei and the counter records a rate of 50000 counts/second, find the decay constant. Assume that the source emits alpha particles uniformly in all directions and the alpha particles fall nearly normally on the window.

An AC source is connected to a diode and a resistor in series. Is the current thorough the resistor AC or DC?

A point source emitting alpha particles is placed at a distance of 1 m from a counter which records any alpha particle falling on its 1 cm² window. If the source contains 6.0 × 10¹⁶ active nuclei and the counter records a rate of 50000 counts/second, find the decay constant. Assume that the source emits alpha particles uniformly in all directions and the alpha particles fall nearly normally on the window.