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 18 of 21

1. Q195 · Original practice · 1 mark
   At the same instant, ball A is dropped from rest and ball B is projected horizontally at $20.0\,\mathrm{m\,s^{-1}}$ from the same height above level ground. Ignore air resistance and ball size. How do their times to reach the ground compare?
   Gravity and motion
2. Q196 · Original practice · 1 mark
   The graph shows the vertical velocity of a projectile, with upward positive. What maximum height does it reach above its launch point?
   Gravity and motion
3. Q197 · Original practice · 1 mark
   A projectile passes a particular height once while rising and once while falling. Its rising velocity is $(12.0\mathbf i+9.00\mathbf j)\,\mathrm{m\,s^{-1}}$, with $\mathbf j$ vertically upward. Ignore drag. What is the change in velocity from the rising passage to the falling passage?
   Gravity and motion
4. Q198 · Original practice · 1 mark
   A block has a downhill weight component of $10.0\,\mathrm N$ and a constant applied force of $6.00\,\mathrm N$ uphill. While sliding, friction has magnitude $2.00\,\mathrm N$. Compare an instant when it slides uphill with a later instant when it slides downhill. Which statement about its acceleration is correct?
   Gravity and motion
5. Q199 · Original practice · 1 mark
   A block of mass $m$ rests on a $30.0^\circ$ incline. A rope exerts force $P$ at $20.0^\circ$ above the incline, as shown. The block remains in contact with the plane. Which expression gives the normal force magnitude?
   Gravity and motion
6. Q200 · Original practice · 1 mark
   The diagram is a top view of an object moving at constant speed around a circle. At P its velocity points left. What is the direction of its instantaneous acceleration?
   Gravity and motion
7. Q201 · Original practice · 1 mark
   A spherical planet has radius $R$. Point A is at altitude $R$ above its surface, and point B is at altitude $2R$. What is the ratio of gravitational field strengths $g_B/g_A$?
   Gravity and motion
8. Q202 · Original practice · 1 mark
   Moon A follows a circular orbit of radius $r$ around a planet of mass $M$. Moon B follows a circular orbit of radius $2r$ around a different planet of mass $4M$. What is $T_B/T_A$?
   Gravity and motion
9. Q203 · Original practice · 1 mark
   A planet sweeps an area of $2.00\times10^{20}\,\mathrm{m^2}$ in $10.0$ days in one part of its elliptical orbit. How long does it take to sweep $3.00\times10^{20}\,\mathrm{m^2}$ elsewhere in the same orbit?
   Gravity and motion
10. Q204 · Original practice · 1 mark
    Two satellites, of masses $m$ and $3m$, follow the same circular orbital radius around a planet of mass $M$. Ignore their influence on the planet and each other. How does their orbital speed compare?
    Gravity and motion
11. Q205 · Original practice · 1 mark
    Two equal positive point charges are at equal horizontal distances from a midpoint. O lies vertically above that midpoint, as shown. What is the direction of the resultant electric field at O?
    Electromagnetism
12. Q206 · Original practice · 1 mark
    An electron moves from electric potential $+80.0\,\mathrm V$ to $+180\,\mathrm V$. Use $q=-1.60\times10^{-19}\,\mathrm C$. What is its change in electrical potential energy?
    Electromagnetism
13. Q207 · Original practice · 1 mark
    A long air-core solenoid is replaced by one with twice as many turns and twice the length. The current is halved. Neglect end effects. What is the new magnetic field strength divided by the original field strength?
    Electromagnetism
14. Q208 · Original practice · 1 mark
    A conducting loop moves right into a uniform magnetic field directed into the page. At the shown instant it is partly inside the field. Viewed as drawn, what is the direction of the induced current?
    Electromagnetism
15. Q209 · Original practice · 1 mark
    Two coils experience the same uniform magnetic field and the same change in orientation over the same time interval. Coil B has twice the number of turns and half the area per turn of coil A. What is the ratio of their induced average EMF magnitudes $|\mathcal E_B|/|\mathcal E_A|$?
    Electromagnetism
16. Q210 · Original practice · 1 mark
    A rectangular panel has rest-frame dimensions $4.00\,\mathrm m$ horizontally and $3.00\,\mathrm m$ vertically. It moves horizontally at $0.600c$ relative to a laboratory. What dimensions does the laboratory measure simultaneously in its own frame?
    Special relativity
17. Q211 · Original practice · 1 mark
    A spacecraft observer measures the interval between two events. Which condition makes that measured interval the proper time interval between those events?
    Special relativity
18. Q212 · Original practice · 1 mark
    A particle of rest mass $m_0$ moves at $0.600c$. A student estimates its momentum as $m_0v$. By what factor must this estimate be multiplied to obtain its relativistic momentum?
    Special relativity
19. Q213 · Original practice · 1 mark
    A traveller completes two equal inertial legs at speed $0.800c$ relative to Earth, returning to Earth. The traveller's clock advances by $3.00$ years on each leg. Neglect the duration of acceleration at departure, turnaround and arrival. How much time elapses on Earth?
    Special relativity
20. Q214 · Original practice · 1 mark
    A system releases energy corresponding to a decrease in its rest mass of $2.00\,\mathrm{mg}$. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$. What energy is released?
    Special relativity
21. Q215 · Original practice · 1 mark
    Two black bodies have peak wavelengths $600\,\mathrm{nm}$ and $1200\,\mathrm{nm}$. What is the temperature of the first divided by the temperature of the second?
    Quantum theory
22. Q216 · Original practice · 1 mark
    A monochromatic beam has fixed power $P$, and its photons each have energy $hf$. Its frequency is doubled while its power stays fixed. What happens to the number of photons arriving per second?
    Quantum theory
23. Q217 · Original practice · 1 mark
    A metal has threshold frequency $f_0$. The incident light frequency changes from $1.50f_0$ to $2.00f_0$. What is the new maximum photoelectron kinetic energy divided by its original value?
    Quantum theory
24. Q218 · Original practice · 1 mark
    The diagram shows four bound energy levels of an atom. An electron starts at the lowest level. Which photon energy cannot excite it to one of the other three shown bound levels? Ignore broadening and multiphoton processes.
    Quantum theory