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 19 of 21

1. Q219 · Original practice · 1 mark
   A non-relativistic electron beam's kinetic energy is increased by a factor of four. How does its de Broglie wavelength change?
   Quantum theory
2. Q220 · Original practice · 1 mark
   In a thin-foil scattering experiment, most positively charged alpha particles pass through, but a small fraction deflect through very large angles. Which conclusion best accounts for both observations?
   Quantum theory
3. Q221 · Original practice · 1 mark
   Quarks $u$ and $d$ have charges $+2e/3$ and $-e/3$, respectively. Which pair forms a meson with charge $+e$?
   The Standard Model
4. Q222 · Original practice · 1 mark
   A neutron is a neutral baryon. Which gives the electric charge and baryon number of an antineutron?
   The Standard Model
5. Q223 · Original practice · 1 mark
   Consider $\mu^-\rightarrow e^-+\bar\nu_e+X$. Which listed particle can be X while conserving electric charge, total lepton number and baryon number?
   The Standard Model
6. Q224 · Original practice · 1 mark
   A down quark changes to an up quark and emits one gauge boson: $d\rightarrow u+X$. Their charges are $-e/3$ and $+2e/3$, respectively. Which X conserves electric charge?
   The Standard Model
7. Q225 · Original practice · 5 marks
   A small ball is launched horizontally at $6.00\,\mathrm{m\,s^{-1}}$ from a platform $19.6\,\mathrm m$ above level ground. A small ground-level catcher moves in the same direction at constant speed $2.00\,\mathrm{m\,s^{-1}}$. At launch it is distance $d$ ahead of the point directly below the ball. Ignore drag and object sizes. Use $g=9.8\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
8. Q226 · Original practice · 5 marks
   A ball is launched from height $1.00\,\mathrm m$ with horizontal velocity $12.0\,\mathrm{m\,s^{-1}}$. A thin vertical screen is $18.0\,\mathrm m$ horizontally from the launch point. Its opening extends from $4.80\,\mathrm m$ to $5.40\,\mathrm m$ above the same ground level. Ignore drag and ball size. Use $g=9.8\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
9. Q227 · Original practice · 6 marks
   A $4.00\,\mathrm{kg}$ block moves uphill on a $30.0^\circ$ incline. A rope pulls with force $18.0\,\mathrm N$ at $20.0^\circ$ above the incline. Friction has magnitude $2.00\,\mathrm N$. The block remains on the plane. Use $g=9.8\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
10. Q228 · Original practice · 6 marks
    A small object moves at constant speed around a horizontal circle of radius $0.500\,\mathrm m$. The graph shows inward resultant force F against $1/T^2$, where T is its period. The fitted line passes exactly through $(1.00\,\mathrm{s^{-2}},3.95\,\mathrm N)$ and $(3.00\,\mathrm{s^{-2}},11.85\,\mathrm N)$. Treat this fit as exact.
    Gravity and motion
11. Q229 · Original practice · 5 marks
    A spherical planet has radius $R=7.00\times10^6\,\mathrm m$ and surface gravitational field strength $8.00\,\mathrm{N\,kg^{-1}}$. A small satellite follows a circular orbit with period $7200\,\mathrm s$. Ignore planetary rotation and other bodies. Use $G=6.67\times10^{-11}\,\mathrm{N\,m^2\,kg^{-2}}$.
    Gravity and motion
12. Q230 · Original practice · 4 marks
    The graph shows gravitational field strength g outside a spherical planet against $1/r^2$, where r is distance from its centre. The exact fitted line passes through $(1.00\times10^{-14}\,\mathrm{m^{-2}},4.00\,\mathrm{N\,kg^{-1}})$. Use $G=6.67\times10^{-11}\,\mathrm{N\,m^2\,kg^{-2}}$.
    Gravity and motion
13. Q231 · Original practice · 5 marks
    Fixed charges $+2.00\,\mu\mathrm C$ and $-2.00\,\mu\mathrm C$ lie $0.300\,\mathrm m$ left and right of O, respectively. P is $0.400\,\mathrm m$ directly above O. Use $k=9.00\times10^9\,\mathrm{N\,m^2\,C^{-2}}$.
    Electromagnetism
14. Q232 · Original practice · 5 marks
    A long air-core solenoid of length $0.300\,\mathrm m$ carries $1.20\,\mathrm A$ and produces an internal field of $4.00\,\mathrm{mT}$. Use $\mu_0=4\pi\times10^{-7}\,\mathrm{T\,m\,A^{-1}}$ and neglect end effects.
    Electromagnetism
15. Q233 · Original practice · 6 marks
    A horizontal wire of length $0.200\,\mathrm m$ is supported by a force sensor in a uniform magnetic field directed into the page. The sensor reads the upward support force. With current $2.00\,\mathrm A$ to the right, its reading is $0.310\,\mathrm N$. Reversing the current gives a reading of $0.470\,\mathrm N$. The wire stays at rest, and the whole stated l…
    Electromagnetism
16. Q234 · Original practice · 5 marks
    A rectangular conducting loop has horizontal width $0.100\,\mathrm m$, vertical height $0.200\,\mathrm m$ and total resistance $2.00\,\Omega$. It moves right at $0.500\,\mathrm{m\,s^{-1}}$ into a uniform $0.300\,\mathrm T$ field directed into the page. Outside the field, B is zero. Ignore self-inductance. Consider an instant when only part of the loop is ins…
    Electromagnetism
17. Q235 · Original practice · 5 marks
    A straight rod has proper length $4.00\,\mathrm m$ and makes an angle of $30.0^\circ$ to the horizontal in its rest frame. The rod moves horizontally at $0.600c$ relative to a laboratory. The laboratory measures both endpoints simultaneously in the laboratory frame. Only the horizontal separation contracts.
    Special relativity
18. Q236 · Original practice · 5 marks
    Two detectors are $600\,\mathrm m$ apart in a laboratory. Unstable particles travel from the first towards the second at $0.800c$ and have a mean proper lifetime of $2.00\,\mu\mathrm s$. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
    Special relativity
19. Q237 · Original practice · 6 marks
    The graph shows momentum p against $\gamma v$ for a particle, where $\gamma=1/\sqrt{1-v^2/c^2}$. The fitted line passes exactly through $(1.00\times10^8\,\mathrm{m\,s^{-1}},3.00\times10^{-19}\,\mathrm{kg\,m\,s^{-1}})$. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
    Special relativity
20. Q238 · Original practice · 5 marks
    A stationary box receives $2.70\,\mathrm{MJ}$ of energy from an external source. During the transfer, $0.900\,\mathrm{MJ}$ escapes as heat. The box is then sealed and retains the remaining energy. Compare its rest mass before the transfer with its rest mass after it is sealed. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
    Special relativity
21. Q239 · Original practice · 6 marks
    A photoelectric experiment plots maximum kinetic energy against $1/\lambda$. The exact fitted line passes through A: $(2.00\times10^6\,\mathrm{m^{-1}},1.50\times10^{-19}\,\mathrm J)$ and B: $(4.00\times10^6\,\mathrm{m^{-1}},5.50\times10^{-19}\,\mathrm J)$. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
    Quantum theory
22. Q240 · Original practice · 5 marks
    Two metals have work functions $W_A=2.00\times10^{-19}\,\mathrm J$ and $W_B=3.00\times10^{-19}\,\mathrm J$. A monochromatic beam must produce a maximum photoelectron kinetic energy of at least $1.00\times10^{-19}\,\mathrm J$ from each metal. Use $h=6.626\times10^{-34}\,\mathrm{J\,s}$ and $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
    Quantum theory
23. Q241 · Original practice · 6 marks
    An atom has the bound energy levels shown. An electron initially in the ground state absorbs one photon and reaches the highest shown level. It then returns to the ground state in exactly two radiative steps. The first emitted photon has energy $6.00\,\mathrm{eV}$. Use $h=6.626\times10^{-34}\,\mathrm{J\,s}$, $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$ and…
    Quantum theory
24. Q242 · Original practice · 5 marks
    An electron beam and a proton beam both have de Broglie wavelength $2.00\times10^{-10}\,\mathrm m$. Both are non-relativistic. Use $h=6.626\times10^{-34}\,\mathrm{J\,s}$, $m_e=9.1093835\times10^{-31}\,\mathrm{kg}$ and $m_p=1.6726219\times10^{-27}\,\mathrm{kg}$.
    Quantum theory