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All Free Physics MCQs with Answers

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13,934 questions · page 670 of 697

13381. The principle of a simple form of mass spectrometer ions is to pass through narrow slits S1 and S2 and into a velocity selector. The ions after passing through the slit S3 are deviated by a uniform magnetic field. The quantities that must remain constant for all ions arriving at the photographic plate are:

  • A. Charged
  • B. Charge/mass(e/m)
  • C. Kinetic energy
  • D. Mass

Explanation: The formula used in mass spectrometry is q/m = v/Br where q is the charge, m is mass, v is velocity, B is magnetic field strength, and r…

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Correct answer: Charge/mass(e/m)

13382. A moving charged particle is surrounded by?

  • A. 1 field
  • B. 3 fields
  • C. 2 fields
  • D. 4 fields

Explanation: A moving charged particle is surrounded by three fields:Electric Field: This field arises due to the charge of the particle itself and…

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Correct answer: 3 fields

13383. A proton is projected with a uniform velocity 'v' along the axis of a current carrying solenoid.

  • A. The proton will be accelerated along the axis.
  • B. The proton path will be circular about the axis.
  • C. The proton moves along a helical path.
  • D. The proton will continue to move with velocity 'v' along the axis.

Explanation: The proton is traveling in the same direction as the solenoid's axis. Because the magnetic field inside the solenoid is homogenous and…

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Correct answer: The proton will continue to move with velocity 'v' along the axis.

13384. A particle of mass moving with velocity V makes head. One elastic collision with another particle of the same mass and initially at rest. The velocity of the first particle after the collision:

  • A. 2V
  • B. -V
  • C. +V
  • D. Zero

Explanation: -V: This option is correct. In an elastic collision, the first particle will experience a change in direction and will have a velocity…

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Correct answer: -V

13385. A object of mass "m" travelling with speed "v" has a head-on collision with another object of mass "m" travelling with speed "v" in the opposite direction, the object sticks together after the collision.What is the total loss of kinetic energy in the collision?

  • A. 0
  • B. 1/2mv2
  • C. mv2
  • D. 2mv2

Explanation: Since there are two equal masses travelling with the equal velocity. Therefore according to the law of conservation of kinetic…

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Correct answer: mv2

13386. A bullets of mass m moving with a velocity v is fired into a large wooden block of mass M. If the bullet remains embedded in the wooden block, the velocity of the system will be:

  • A. Option A
  • B. Option B
  • C. Option C
  • D. Option D

Explanation: Since there is no extra force other than the action and reaction force so the linear momentum should be conserved.Suppose the system moves…

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Correct answer: Option B

13387. A body of mass 2kg collides with a wall with speed 100 m s-1 and rebounds with the same speed the force exerted on the wall is 2 x 10^4 N. The time of contactis:

  • A. 1/50 Sec
  • B. 1/25 Sec
  • C. 1/60 Sec
  • D. 1 Sec

Explanation: F=mv/t2 x 104 N =2*(100-(-100))/tt=1/50 s

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Correct answer: 1/50 Sec

13388. The following reaction might be used for controlled nuclear fusion 3 Li7 + 1H2 ➔ 2(2He4) + X? What is the particle X?

  • A. An alpha-particle
  • B. An electron
  • C. A neutron
  • D. A proton

Explanation: Without going into deep discussions An easy way to solve such questions, is to balance charge(atomic number) and mass on both sides For…

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Correct answer: A neutron

13389. 1 atomic mass unit (amu) in terms of energy is nearly equal to:

  • A. 931 KeV
  • B. 931 MeV
  • C. 39 MeV
  • D. 139 KeV

Explanation: The correct answer is Option B: 931 MeV. By utilizing the mass-energy equivalence formula E=mc^2, we calculate that 1 atomic mass unit…

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Correct answer: 931 MeV

13390. Fast neutrons can be slowed down by collisions with:

  • A. Electrons
  • B. Protons
  • C. Phonons
  • D. Photons

Explanation: A nuclear reactor is a device in which nuclear reactions are initiated,maintained,and controlled.It works on the principle of controlled…

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Correct answer: Protons

13391. Cadmium rods are used in a nuclear reactor for :

  • A. Slowing down fast neutrons
  • B. Speeding up slow neutrons
  • C. Absorbing fast neutrons
  • D. Regulating the power evel of the reactor

Explanation: Cadmium rods are used in a nuclear reactor for absorbing fast neutrons.

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Correct answer: Absorbing fast neutrons

13392. A nucleus emits gamma (γ) photon what happens to its atomic number and actual mass:

  • A. Atomic number and actual mass remain unchanged
  • B. atomic number and actual mass both decrease
  • C. atomic number and actual mass both increase
  • D. atomic number remains the same but the actual mass decrease

Explanation: Radioactivity is the phenomena in which an unstable nuclei emits alpha particle, beta particle or gamma ray in order to achieve stability.

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Correct answer: Atomic number and actual mass remain unchanged

13393. Neutrons can be slowed down if the stationary targets are:

  • A. Alpha particles
  • B. Photons
  • C. Protons
  • D. Atoms

Explanation: Neurons can be slowed down if they collide with stationary protons. This process is called neutron moderation, and it involves…

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Correct answer: Protons

13394. The amount of energy required to break the nucleus into constituent nucleons is called;

  • A. Excitation energy
  • B. Ionization energy
  • C. Binding energy
  • D. Work function

Explanation: Binding energy is the amount of energy required to break a nucleus into its nucleons (protons and neutrons).

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Correct answer: Binding energy

13395. A fission reaction can be produced by:

  • A. fast neutrons
  • B. slow neutrons
  • C. thermal neutrons
  • D. all of these

Explanation: Fission occurs when a neutron bumps into a larger atom, forcing it to excite and split into two smaller atoms, known as fission products.

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Correct answer: fast neutrons

13396. The expression for binding energy is:

  • A. EB = fh
  • B. EB = [(ZMP + N Mn) - ZMA] C2
  • C. EB = ZMP C2 + N Mn ZMA C2
  • D. EB = ZMP + N Mn - M C2

Explanation: The correct expression for nuclear binding energy is EB = [(ZMP + N Mn) - ZMA] C2.

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Correct answer: EB = [(ZMP + N Mn) - ZMA] C2

13397. In a nuclear fission reaction, what molecules are produced?

  • A. Neutrons
  • B. Protons
  • C. Electrons
  • D. Alpha particles

Explanation: When a nucleus fissions, it splits into several smaller fragments. These fragments, or fission products, are about equal to half the…

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Correct answer: Neutrons

13398. From the following, which one particle belongs to lepton group:

  • A. Neutrinos
  • B. Protons
  • C. Neutrons
  • D. Mesons

Explanation: Neutrinos are subatomic particles that belong to the family of elementary particles known as leptons.

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Correct answer: Neutrinos

13399. In liquid metal fast breeder reactor the moderator used is:

  • A. Graphite
  • B. Heavy water
  • C. Boron rods
  • D. Not required

Explanation: No moderator is used in the breeder reactor since fast neutrons are more efficient in transmuting U-238 to Pu-239.

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Correct answer: Not required

13400. Binding energy of nucleus is the energy that must be supplied to:

  • A. Remove nucleons
  • B. Remove an alpha-particle
  • C. Remove a B-particle
  • D. Separate the nucleus into its constituent nucleons

Explanation: When nuclear reactions occur, there is always a mass defect (products have lower mass than reactants).

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Correct answer: Separate the nucleus into its constituent nucleons
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