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 20 of 21

1. Q243 · Original practice · 5 marks
   The diagram shows an electron and its antiparticle X annihilating to produce two photons. In the centre-of-momentum frame the initial total energy is $1.60\,\mathrm{MeV}$ and the initial total momentum is zero. Use $h=6.626\times10^{-34}\,\mathrm{J\,s}$, $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$ and $1.00\,\mathrm{eV}=1.60\times10^{-19}\,\mathrm J$.
   The Standard Model
2. Q244 · Original practice · 5 marks
   A proton and an antiproton collide with enough total energy for any listed final state. Consider the three candidate channels below. Use electric charge, baryon number B and total lepton number L only; passing these tests does not guarantee that a process occurs.

   | Channel | Final particles | | --- | --- | | I | $n+n$ | | II | $e^-+\nu_e$ | | III |…
   The Standard Model
3. Q245 · Original practice · 4 marks
   A survey robot travels $6.00\,\mathrm m$ east, then $8.00\,\mathrm m$ north. Use the supplied grid; each square represents $1.00\,\mathrm m$.
   Gravity and motion
4. Q246 · Original practice · 4 marks
   A ball is projected with initial components $u_x=8.00\,\mathrm{m\,s^{-1}}$ and $u_y=9.80\,\mathrm{m\,s^{-1}}$. The schematic path marks launch A, apex B and return to launch height C. Ignore drag; use $g=9.80\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
5. Q247 · Original practice · 5 marks
   A $2.00\,\mathrm{kg}$ block slides down a $30.0^\circ$ incline. A rope pulls it uphill with tension $3.00\,\mathrm N$; kinetic friction has magnitude $1.00\,\mathrm N$. Use $g=9.80\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
6. Q248 · Original practice · 1 mark
   A robot moves at constant speed around a circle of radius $2.00\,\mathrm m$, completing one revolution in $8.00\,\mathrm s$. During a half revolution, which pair gives its average speed and the magnitude of its average velocity?
   Gravity and motion
7. Q249 · Original practice · 5 marks
   A $4.00\,\mathrm{kg}$ block rests on a smooth $30.0^\circ$ incline. It is attached by a massless string over a frictionless pulley to a hanging mass $m$. The system is in equilibrium. Use $g=9.80\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
8. Q250 · Original practice · 5 marks
   A small toy car of mass $0.250\,\mathrm{kg}$ moves uniformly around a horizontal circular track of radius $0.800\,\mathrm m$. A guide supplies an inward horizontal force of $1.25\,\mathrm N$. The track is $1.25\,\mathrm m$ above level ground. At P the guide ends and the car leaves horizontally. Ignore drag; use $g=10.0\,\mathrm{m\,s^{-2}}$.
   Gravity and motion
9. Q251 · Original practice · 1 mark
   Two planets orbit the same star on elliptical paths with the same semi-major axis but different eccentricities. Neglect their masses relative to the star. Which statement follows from Kepler's laws?
   Gravity and motion
10. Q252 · Original practice · 4 marks
    The diagram shows a spherical planet and a satellite at P in a circular orbit. The planet has radius $R$; P is at radius $2R$ from its centre. Ignore other gravitational fields.
    Gravity and motion
11. Q253 · Original practice · 3 marks
    A long straight wire carries current directly out of the page, shown by a dot in a circle.
    Electromagnetism
12. Q254 · Original practice · 3 marks
    A bar magnet is shown. Its north pole is on the left and its south pole is on the right.
    Electromagnetism
13. Q255 · Original practice · 3 marks
    The diagram shows opposing flat magnet poles, N on the left and S on the right. A straight wire in the central gap carries conventional current out of the page. Treat the central gap field as uniform.
    Electromagnetism
14. Q256 · Original practice · 4 marks
    A long air-core solenoid has $900$ turns, length $0.450\,\mathrm m$ and current $0.800\,\mathrm A$. Viewed from its left end, the current circulates counterclockwise, as shown. Use $\mu_0=4\pi\times10^{-7}\,\mathrm{T\,m\,A^{-1}}$ and neglect end effects.
    Electromagnetism
15. Q257 · Original practice · 1 mark
    Two small identical spheres carry equal positive charges $q$. Their centres are $0.200\,\mathrm m$ apart and they repel with force $0.0900\,\mathrm N$. Use $k=9.00\times10^9\,\mathrm{N\,m^2\,C^{-2}}$. What is $q$?
    Electromagnetism
16. Q258 · Original practice · 6 marks
    A U-shaped magnet rests on a digital scale. A horizontal wire is held above it by a separate support and does not touch it. A $0.100\,\mathrm m$ wire segment lies perpendicular to the field. The graph shows scale reading $m_s$ in kg against conventional current $I$. For positive $I$, the magnetic force on the wire is upward. Use $g=9.80\,\mathrm{m\,s^{-2}}$.
    Electromagnetism
17. Q259 · Original practice · 3 marks
    A negatively charged oil drop of mass $3.20\times10^{-15}\,\mathrm{kg}$ is held stationary in a uniform downward electric field of $4.90\times10^4\,\mathrm{N\,C^{-1}}$. Use $g=9.80\,\mathrm{m\,s^{-2}}$ and $e=1.60\times10^{-19}\,\mathrm C$.
    Electromagnetism
18. Q260 · Original practice · 4 marks
    A $50$-turn stationary coil has the per-turn flux graph shown. Positive flux is out of the page. Positive EMF drives counterclockwise conventional current, corresponding to the outward normal. Ignore self-inductance.
    Electromagnetism
19. Q261 · Original practice · 4 marks
    A $200$-turn generator coil has area $5.00\times10^{-3}\,\mathrm{m^2}$ per turn in a uniform $0.300\,\mathrm T$ field. It rotates uniformly. In $0.0500\,\mathrm s$, the angle between its area normal and the field changes from $0^\circ$ to $90.0^\circ$.
    Electromagnetism
20. Q262 · Original practice · 4 marks
    An ideal transformer has $500$ primary turns and $100$ secondary turns. Its primary is connected to a $120\,\mathrm V$ rms AC supply.
    Electromagnetism
21. Q263 · Original practice · 1 mark
    A loop has area $0.0200\,\mathrm{m^2}$ in a uniform field of magnitude $0.400\,\mathrm T$. Its plane is parallel to the field. Which pair gives magnetic flux density and magnetic flux through the loop?
    Electromagnetism
22. Q264 · Original practice · 2 marks
    An antenna charge oscillates vertically. At a distant point, the electromagnetic wave travels horizontally to the right and its electric field is momentarily vertically upward.
    Electromagnetism
23. Q265 · Original practice · 3 marks
    A spacecraft travels toward a station at $0.500c$ and emits light toward it in vacuum. Both observers are inertial.
    Special relativity
24. Q266 · Original practice · 5 marks
    A ladder has proper length $10.0\,\mathrm m$ and a barn has proper length $8.00\,\mathrm m$. The ladder moves right at $0.800c$ relative to the barn. In the barn frame, both doors close briefly and simultaneously while the whole ladder is inside. They reopen before the ladder reaches either door. No collision occurs.
    Special relativity