Physics 9702 · AS & A Level · Damped and forced oscillations, resonance
Damped and forced oscillations, resonance — practice question
A bar magnet with mass $250\,\text{g}$ is hung from the free end of a spring, as shown in Fig. 3.1. One pole of the magnet lies close to the middle of a coil of wire. The coil is linked in series with a resistor and a switch. The switch is open. The magnet is moved vertically and then left to oscillate, with one pole kept inside the coil. The other pole stays outside the coil. At time $t = 0$, the magnet is oscillating freely as it moves through its equilibrium position. At time $t = 6.0\,\text{s}$, the switch in the circuit is closed.
(a(i))[2]
For the oscillating magnet, use the data in Fig. 3.2 to calculate the frequency $f$, correct to two significant figures.
(a(ii))[3]
For the oscillating magnet, use the information in Fig. 3.2 to calculate the energy of the oscillations over the interval from time $t = 0$ to time $t = 6.0\,\text{s}$.
(b(i))[2]
State Faraday’s law for electromagnetic induction.
(b(ii))[3]
Use Faraday’s law and energy conservation to explain why the amplitude of the magnet’s oscillations decreases after time $t = 6.0\,\text{s}$.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “period found from, for example, $6/2.5$” …