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

The pressure acting on a submarine is 3 × 10⁵ Pa at a certain depth. If the depth is doubled, the percentage increase in the pressure acting on the submarine would be ______.

(Assume that atmospheric pressure is 1 × 10⁵ Pa density of water is 10³ kg m^–3, g = 10 ms^–2)

The least count of the main scale of a vernier callipers is 1 mm . Its vernier scale is divided into 10 divisions and coincide with 9 divisions of the main scale. When jaws are touching each other, the 7^th division of vernier scale coincides with a division of main scale and the zero of vernier scale is lying right side of the zero of main scale. When this vernier is used to measure length of cylinder the zero of the vernier scale between 3.1 cm and 3.2 cm and 4^th VSD coincides with a main scale division. The length of the cylinder is: (VSD is vernier scale division)

An electric fan has blades of length 30 cm as measured from the axis of rotation. If the fan is rotating at 1200 r.p.m. The acceleration of a point on the tip of the blade is about:

A conducting loop of resistance R and radius r has its centre at the origin of the coordinate system in a magnetic field of induction B. When it is rotated about y-axis through 90°, the net charge flown in the loop is directly proportional to:

The main scale of a spectrometer is divided into 720 division in all. If circular vernier scale consists of 30 divisions, the least count of the instrument is ______.

(Given: 30 vernier divisions coincide with 29 main scale divisions)

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 ______.