A-Level Physics Flashcards: Mechanics and Waves

A-Level Physics — Mechanics and Waves Flashcards

20 flashcards with spaced repetition. Press Space to flip, then rate your recall (1—4).

What These Flashcards Cover

These flashcards span the mechanics and waves content that forms the backbone of A-Level Physics. Mastery here underpins nearly every other topic.

Key areas:

• SUVAT Equations: The four equations of motion under constant acceleration. $v = u + at$, $s = ut + \frac{1}{2}at^{2}$, $v^{2} = u^{2} + 2as$, $s = \frac{1}{2}(u+v)t$. Remember: these only work when acceleration is constant.
• Newton’s Laws: First law (equilibrium), second law ($F = ma$), third law (equal and opposite). Always specify the object and the agent when stating forces. Free-body diagrams are essential.
• Momentum and Impulse: $p = mv$. Impulse $J = F\Delta t = \Delta p$. In a collision, total momentum is conserved if no external resultant force acts. For elastic collisions, kinetic energy is also conserved.
• Simple Harmonic Motion (SHM): Acceleration is proportional to displacement and directed towards the equilibrium position: $a = -\omega^{2}x$. Key equations: $x = A\cos(\omega t)$, $v = \pm\omega\sqrt{A^{2} - x^{2}}$, $T = \frac{2\pi}{\omega}$.
• Wave Properties: $v = f\lambda$. Transverse vs longitudinal. Displacement-position and displacement-time graphs. The intensity of a wave is proportional to the square of its amplitude: $I \propto A^{2}$.
• Quantum Physics: Photon energy $E = hf = \frac{hc}{\lambda}$. The photoelectric effect: $hf = \phi + E_{k,\text{max}}$. Work function $\phi$ is the minimum energy to remove an electron. Threshold frequency $f_0 = \frac{\phi}{h}$.
• Thermal Physics: Internal energy is the sum of kinetic and potential energies of molecules. $Q = mc\Delta\theta$ for temperature changes; $Q = mL$ for phase changes. The first law: $\Delta U = Q - W$.

Intuition

Kinematics is like reading a journey tracker: displacement tells you where you are, velocity tells you how fast and in what direction, and acceleration tells you how that velocity is changing. SUVAT is just the maths that links these quantities when the acceleration stays the same.

For SHM, think of a mass on a spring. The further you pull it from equilibrium, the harder the spring pulls it back. That restoring force creates an oscillation where energy shuttles between kinetic and potential forms, like a pendulum swinging.

Waves are how energy travels without matter moving overall. Imagine doing “the wave” in a stadium: each person only moves up and down, but the pattern travels across the crowd.

Common Pitfalls

1. Using SUVAT for non-constant acceleration. If acceleration changes (e.g. air resistance, varying force) you cannot use SUVAT. You would need to integrate or use energy methods.
2. Confusing displacement-time and velocity-time graphs. The gradient of a displacement-time graph is velocity; the gradient of a velocity-time graph is acceleration. The area under a velocity-time graph is displacement.
3. Forgetting that kinetic energy is not conserved in inelastic collisions. Momentum is always conserved (if no external force), but in a perfectly inelastic collision the objects stick together and maximum KE is lost.
4. Misidentifying the threshold frequency. Below $f_0$, no electrons are emitted regardless of intensity. Increasing intensity only increases the number of electrons emitted (above $f_0$), not their maximum KE.

Cross-References

• Electricity: Mechanics connects to electricity
• Nuclear: Nuclear physics uses mechanics
• Waves: Oscillations link mechanics and waves