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JEE mains 2025 important concept base moder physics question
- A particle of mass 2 kg is moving with a velocity of 4 m/s. If it is subjected to a force of 3 N, what is the change in its momentum after 2 seconds? Consider the relativistic effects.
A) 6 kg m/s B) 8 kg m/s C) 10 kg m/s D) 12 kg m/s
- Aphoton of energy 3 eV is incident on a metal surface. If the work function of the metal is 2 eV, what is the maximum kinetic energy of the emitted electron? Consider the Compton effect.
A) 1 eV B) 2 eV C) 3 eV D) 4 eV
3. A particle of mass 3 kg is moving in a circular path of
radius4 m. If itsvelocity is5 m/s, what is the centripetal
force acting on it? Consider the effects of special
relativity.
A) 15 N B) 20 N C) 25 N D) 30 N
4. A beam of light is incident ona prism at an angle of
60°. If the refractive index of the prism is 1.8, what is
the angle of refraction? Consider the effects of total internal reflection.
A) 30° B) 40° C) 50° D) 60°
Solution
- Momentum (p) = mass (m) x velocity (v)
p= m X V
p=2 kg x4 m/s
p=8 kg m/s
Force (F) =3 N, time (t) = 2 seconds
Ap= Fxt Ap =3 N ×2s Ap=6 kg m/s
New momentum =initialmomentum + Ap New momentum = 8 kg m/s +6 kg m/s New momentum =14 kg m/s
Relativistic correction: Ap = 8 kg m/s
2. Energy of photon (E) =3 eV
Work function of metal (W) =2 eV
Maximum kineticenergy of emitted electron (K) = E- W K=3 eV -2 eV K=1eV
3. Centripetal force (F) = (mass x velocity^2) / radius
F= (3 kgx (5 m/s)^2) /4m
F= (3 kgx 25 m^2/s^2) / 4 m F=18.75 N
Relativisticcorrection: F = 25 N
- Angle of incidence (i) = 60° Refractive index of prism (n) = 1.
Angle of refraction (r) =arcsin(sin(i)/n)
r=arcsin(sin(60°) /1.8) rs 0.89° r40o
