JEE Advanced 2021 physics questions with solutions

Showing 1–10 of 26 questions

• Multi-correctmediumRotational Motioncombined translatory and rotatory motion ,Pure rolling motion

  A horizontal force F is applied at the center of mass of a cylindrical object of mass m and radius R, perpendicular to its axis as shown in the figure. The coefficient of friction between the object and the ground is μ. The center of mass of the object has an acceleration a. The acceleration due to gravity is g. Given that the object rolls without slipping, which of the following statement(s) is(are) correct?

  

  Select all that apply

  • Option A

    For the same F, the value of a does not depend on whether the cylinder is solid or hollow.

  • Option B

    For a solid cylinder, the maximum possible value of a is 2μg.

  • Option C

    The magnitude of the frictional force on the object due to the ground is always μmg.

  • Option D

    For a thin-walled hollow cylinder, 2 F a m =.

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• NumericmediumMagnetic effect of current

  An α-particle (mass 4 amu, charge +2e) and a singly charged sulfur ion (mass 32 amu, charge +e) are initially at rest. They are accelerated through the same potential V and enter a uniform magnetic field perpendicular to their velocities. If their orbit radii are rα and rₛ respectively, find rₛ/rα.

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• Multi-correcteasyWave Motion

  A source approaches the open end of a stationary pipe of length L with speed u and emits frequency fₛ. The far end is closed. Sound speed is v and f₀ is the pipe fundamental. Which combinations of u and fₛ produce resonance?

  Select all that apply

  • Option A

    u = 0.8v, fₛ = f₀

  • Option B

    u = 0.8v, fₛ = 2f₀

  • Option C

    u = 0.8v, fₛ = 0.5f₀

  • Option D

    u = 0.5v, fₛ = 1.5f₀

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• NumericmediumRotational Motioncombined translatory and rotatory motion ,Pure rolling motion

  A thin rod of mass M and length a rotates horizontally about a fixed vertical axis through O with angular velocity Ω. A thin disc of mass M and radius a/4 is pivoted on the rod with its centre a/4 from the free end and rotates about its own vertical axis with angular velocity 4Ω. The total angular momentum about O is (nMΩa²)/48. Find n.

  

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• NumericmediumAC Circuits

  In a circuit, a metal filament lamp is connected in series with a capacitor of capacitance CuF across a 200V, 50Hz supply. The power consumed by the lamp is 500W while the voltage drop across it is 100V. Assume that there is no inductive load in the circuit. Take rms values of the voltages. The magnitude of the phase-angle (in degrees) between the current and the supply voltage is j. Assume,

  1V3 =5.The value of j is______.

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• NumericmediumPhotoelectric effect and dual nature of matter

  In a photoemission experiment, Kₚ = 2KQ = 2Kᵣ. The same photon source is used for P and Q, but a different source for R. Work functions are 4.0, 4.5 and 5.5 eV, respectively. Find the photon energy used for R, in eV.

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• NumericmediumThermodynamics

  A small object is placed at the centre of a large evacuated spherical container maintained at 0 K. The object's temperature falls from 200 K at t=0 to 100 K at t₁ and to 50 K at t₂. Assume both object and container are ideal black bodies and the object's heat capacity is temperature-independent. Find t₂/t₁.

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• Multi-correctmediumMagnetic effect of current

  Two concentric circular loops, one of radius R and the other of radius 2R, lie in the xy-plane with the origin as their common center, as shown in the figure. The smaller loop carries current I₁ in the anti-clockwise direction and the larger loop carries current I₂ in the clockwise direction, with I₂ > 2I1. B⃗ (x, y) denotes the magnetic field at a point (x, y) in the xy-plane. Which of the following statement(s) is(are) correct?

  

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  • Option A

    B⃗(x,y) is perpendicular to the xy-plane at every point in the plane.

  • Option B

    |B⃗(x,y)| depends on x and y only through r=√(x²+y²).

  • Option C

    |B⃗(x,y)| is nonzero at all points for r<R.

  • Option D

    B⃗ points outward from the xy-plane at every point between the two loops.

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• NumericmediumSimple Harmonic Motion

  A bob of mass 0.1 kg is attached to a spring of natural length l₀=0.1 m. k₁=0.009 N m⁻¹ for l>l₀ and k₂=0.016 N m⁻¹ for l<l₀. It is released from l=0.15 m. If full period is T=nπ s, find the nearest integer n.

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• Multi-correctdifficultGeometrical opticslaw of refraction and total internal reflection

  A wide slab consisting of two media of refractive indices n₁ and n₂ is placed in air as shown in the figure. A ray of light is incident from medium n₁ to n₂ at an angle θ, where sin θ is slightly larger than 1/n₁. Take refractive index of air as 1. Which of the following statement(s) is(are) correct?

  

  Select all that apply

  • Option A

    The light ray enters air if n₂ = n₁

  • Option B

    The light ray is finally reflected back into the medium of refractive index n₁ if n₂ < n₁

  • Option C

    The light ray is finally reflected back into the medium of refractive index n₁ if n₂ > n₁

  • Option D

    The light ray is reflected back into the medium of refractive index n₁ if n₂ = 1

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