JEE Main entrance exam Question Bank Solutions for Physics (JEE Main)

Four particles A, B, C, and D with masses m_A = m, m_B = 2m, m_C = 3m, and m_D = 4m are at the corners of a square. They have accelerations of equal magnitude with directions as shown. The acceleration of the centre of mass of the particles is ______.

One centimetre on the main scale of vernier callipers is divided into ten equal parts. If 10 divisions of vernier scale coincide with 8 small divisions of the main scale, the least count of the callipers is ______.

A vernier calliper has 20 divisions on the vernier scale, which coincide with 19 on the main scale. The least count of the instrument is 0.1 mm. The main scale divisions are of ______.

Two students measure the weight of a 10 Kg mass using a spring balance and record these readings as:

A: 10Kg, 10Kg, 10.5Kg, 10.5Kg, 9.5Kg

B: 10Kg, 10.1Kg, 10.1Kg, 9.8Kg, 9.9Kg

Then

Two streams of photons, possessing energies equal to five and ten times the work function of metal are incident on the metal surface successively. The ratio of maximum velocities of the photoelectron emitted, in the two cases respectively, will be:

An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon will be:

The average energy for molecules in one degree of freedom is ______.

The speed of a wave in a string is 20 m/s and the frequency is 50 Hz. The phase difference between two points on the string 10 cm apart will be ______.

A thin circular ring of mass M and radius R is rotating with a constant angular velocity of 2 rads^-1 in a horizontal plane about an axis vertical to its plane and passing through the center of the ring. If two objects each of mass m be attached gently to the opposite ends of a diameter of the ring, the ring will then rotate with an angular velocity (in rads^-1).

A pressure pump has a horizontal tube with a cross-sectional area of 10 cm² for the outflow of water at a speed of 20 m/s. The force exerted on the vertical wall just in front of the tube which stops water horizontally flowing out of the tube, is ______.

[given: density of water = 1000 kg/m³]

A submarine experiences a pressure of 5.05 × 10⁶ Pa at depth of d₁ in the sea. When it goes further to a depth of d₂, it experiences a pressure of 8.08 × 10⁶ Pa. Then d₁ - d₂ is approximately (density of water = 10³ kg/m³ and acceleration due to gravity = 10 ms^-2) ______.

Which statements are correct about degrees of freedom?

1. A molecule with n degrees of freedom has n² different ways of storing energy.
2. Each degree of freedom is associated with `1/2`RT average energy per mole.
3. A monoatomic gas molecule has 1 rotational degree of freedom whereas the diatomic molecule has 2 rotational degrees of freedom.
4. CH₄ has a total of 6 degrees of freedom.

Choose the correct answer from the option given below:

A gas has n degrees of freedom. The ratio of the specific heat of the gas at constant volume to the specific heat of the gas at constant pressure will be ______.

An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure (C_P) and at constant volume (C_v) is ______.

Two massless springs with spring constants 2k and 9k carry 50 g and 100 g masses at their free ends. These two masses oscillate vertically such that their maximum velocities are equal. Then, the ratio of their respective amplitudes will be ______.

A transverse wave is represented by y = 2sin (ωt - kx) cm. The value of wavelength (in cm) for which the wave velocity becomes equal to the maximum particle velocity, will be ______.

A small speaker delivers 2W of audio output. At what distance from the speaker will one detect 120 dB intensity sound?

[Given reference intensity of sound as 10^-12W/m²]

Two stars of masses m and 2m at a distance d rotate about their common centre of mass in free space. The period of revolution is ______.

A hydraulic press can lift 100 kg when a mass 'm' is placed on the smaller piston. It can lift ______ kg when the diameter of the larger piston is increased by 4 times and that of the smaller piston is decreased by 4 times keeping the same mass 'm' on the smaller piston.

The resistance R = `"V"/"I"`, where V = (50 ± 2) V and I = (20 ± 0.2)A. The percentage error in R is 'x' %. 

The value of x to the nearest integer is ______.