Physics questions and solutions

Browse original practice and official past-paper questions. Each question has its own link, with its source and worked solution.

498 questions · Page 15 of 21

1. Q123 · Original practice · 1 mark
   The energy equivalent of $2.0$ micrograms of mass is closest to
   Special relativity
2. Q124 · Original practice · 1 mark
   A $+3.0$ microC charge moves through a potential difference of $-20\,\mathrm{V}$. Its change in electric potential energy is
   Electromagnetism
3. Q125 · Original practice · 1 mark
   Planet B orbits the same star at $9$ times Planet A’s orbital radius. The ratio $\frac{T_B}{T_A}$ is
   Gravity and motion
4. Q126 · Original practice · 3 marks
   A rescue capsule is launched from a $3.0\,\mathrm{m}$ high platform at $24.0\,\mathrm{m}\,\mathrm{s}^{-1}$ and $40.0^{\circ}$ above the horizontal. Air resistance is negligible.
   Gravity and motion
5. Q127 · Original practice · 3 marks
   A $0.250\,\mathrm{m}$ conductor carries $4.20 A$ horizontally west through a uniform $0.360\,\mathrm{T}$ magnetic field directed vertically upward.
   Electromagnetism
6. Q128 · Original practice · 5 marks
   An unstable particle has a proper mean lifetime of $1.60$ microseconds and moves at $0.940c$ relative to a laboratory.
   Special relativity
7. Q129 · Original practice · 9 marks
   A photoelectric experiment gives the following stopping potentials: $\frac{f}{10^{14} Hz} = 5.5, 6.5, 7.5, 8.5$ and $\frac{V_s}{V} = 0.18, 0.59, 1.01, 1.43$. Treat the trend as linear.
   Quantum theory
8. Q130 · Original practice · 11 marks
   A proton in a nucleus undergoes $\beta$-plus decay, represented at the nucleon level by $p \to n + e+ +$ nu$_e$.
   The Standard Model
9. Q131 · Original practice · 5 marks
   A drone moves with horizontal velocity components $6.0\,\mathrm{m}\,\mathrm{s}^{-1}$ east and $8.0\,\mathrm{m}\,\mathrm{s}^{-1}$ north before releasing a package from a height of $45\,\mathrm{m}$. Neglect air resistance.
   Gravity and motion
10. Q132 · Original practice · 5 marks
    A positive ion passes undeflected through crossed electric and magnetic fields. The electric field is $3.60\times10^{4}\,\mathrm{N}\,\mathrm{C}^{-1}$ upward and the magnetic field is $0.120\,\mathrm{T}$ out of the page.
    Electromagnetism
11. Q133 · Original practice · 5 marks
    Two flashes occur at the same point in a spacecraft frame, separated by $4.00\,\mathrm{s}$ on the spacecraft clock. The spacecraft moves at $0.800c$ relative to Earth.
    Special relativity
12. Q134 · Original practice · 7 marks
    Electrons accelerated through $150\,\mathrm{V}$ strike a crystal. Assume non-relativistic motion.
    Quantum theory
13. Q135 · Original practice · 5 marks
    A neutron is described by valence quarks udd.
    The Standard Model
14. Q136 · Original practice · 8 marks
    A moon of radius $1.74\times10^{6}\,\mathrm{m}$ and mass $7.35\times10^{22}\,\mathrm{kg}$ has a research satellite in a circular orbit $100\,\mathrm{km}$ above its surface.
    Gravity and motion
15. Q137 · Original practice · 5 marks
    A $250$-turn square coil of side $0.080\,\mathrm{m}$ is initially perpendicular to a $0.300\,\mathrm{T}$ magnetic field directed into the page. The field falls uniformly to $0.060\,\mathrm{T}$ in $0.120\,\mathrm{s}$.
    Electromagnetism
16. Q138 · Original practice · 4 marks
    A $120\,\mathrm{m}$ spacecraft has this length in its own rest frame. Earth observers measure it moving at $0.600c$.
    Special relativity
17. Q139 · Original practice · 6 marks
    For hydrogen, $E_n=-\frac{13.6\,\mathrm{eV}}{n^{2}}$. An atom emits a photon in the transition $n=5$ to $n=2$.
    Quantum theory
18. Q140 · Original practice · 1 mark
    A charged particle moves through a low-pressure gas in a region of uniform magnetic field directed into the page. Collisions with gas atoms cause the particle to lose kinetic energy, so its speed decreases along its path.

    The track of the particle between points P and Q is shown.

    Which row correctly identifies the sign of the charge on the particle and…
    Magnetic fields
19. Q141 · Original practice · 9 marks
    A ball is kicked from level ground and lands on the flat roof of a building. Air resistance is negligible.

    The graph shows the speed of the ball from the instant it is kicked until the instant it lands on the roof.
    Projectile motion
20. Q142 · Original practice · 1 mark
    A spaceship carries a light clock: a light pulse travels between two mirrors that are 1.50 m apart, measured perpendicular to the direction of motion of the spaceship. The mirrors are 1.50 m apart for observers on the spaceship and for observers on Earth.

    The diagram shows the path of one pulse from the bottom mirror to the top mirror, as described by each…
    Special relativity
21. Q143 · Original practice · 11 marks
    A rectangular coil of 500 turns is 4.0 cm wide and 5.0 cm high. The coil is released from rest with its lower edge level with the top boundary of a region of uniform magnetic field directed into the page, as shown. The field region is wider than the coil and has a vertical thickness $D$.

    The coil falls with its plane perpendicular to the field and with its…
    Electromagnetic induction
22. Q144 · Original practice · 11 marks
    In the Bohr model of the hydrogen atom, a single electron moves at constant speed $v$ in a circular orbit of radius $r$ around a stationary proton. The electric force between the proton and the electron provides the centripetal force.

    In the $n$th allowed orbit, the angular momentum of the electron satisfies

    $$mvr = \frac{nh}{2\pi}$$

    where $m$ is the mass…
    Quantum theory
23. Q145 · Original practice · 1 mark
    A ball is projected at $24.0\,\mathrm{m\,s^{-1}}$ at $60.0^\circ$ above horizontal. Ignore air resistance. Which is its velocity at the highest point?
    Gravity and motion
24. Q146 · Original practice · 1 mark
    A block rests on a smooth incline at angle $\theta$. A force $P$ is applied parallel to the incline, as shown. What is the magnitude of the normal force?
    Gravity and motion