What this covers
This standard sits within Waves. In a one-to-one lesson we make sure the idea is clear first, then move straight to applying it in the exact way SPM asks, with correct units and full working.
How it is examined
It can appear in Paper 1 (objective) and Paper 2 (structured), and where an experiment applies, in Paper 3. We do not predict which questions appear; we prepare the technique for all of them.
A common mistake
How to study it
Learn the definition precisely, practise one or two SPM-style questions with full working, and link it to the rest of Waves. If it keeps costing marks, a one-to-one lesson fixes exactly that.
Waves · Formulas · Exam Papers
What you need to know
Damping occurs when the amplitude of an oscillating system decreases over time due to energy loss, usually as heat, to the surroundings. External damping results from resistive forces outside the system, such as air resistance or friction acting on a swinging pendulum.
Internal damping arises from within the material itself, such as the internal friction in a vibrating spring that gradually converts kinetic and potential energy into heat. Every oscillating system has a natural frequency, the frequency at which it vibrates freely once disturbed, without any external driving force.
Resonance occurs when a system is driven by an external periodic force whose frequency matches the natural frequency of the system, causing the amplitude of oscillation to become maximum. At resonance, energy is transferred most efficiently from the driving force to the oscillating system.
Classic demonstrations include Barton's pendulums, where only the pendulum with a length matching the driver oscillates with large amplitude, and musical instruments, where sound boxes resonate at specific frequencies to amplify particular notes produced by strings or air columns.
Worked example
Consider a pendulum demonstration using Barton's pendulums, where several pendulums of different lengths hang from a common string, together with a driver pendulum of a specific length. When the driver pendulum is set swinging, it transmits small periodic forces through the supporting string to all the other pendulums.
Only the pendulum whose length is the same as the driver pendulum has the same natural frequency as the driving frequency, so it absorbs energy most effectively and swings with the largest amplitude, demonstrating resonance. The other pendulums, with different lengths and therefore different natural frequencies, show much smaller amplitudes because their natural frequency does not match the driving frequency.
To describe this as a labelled diagram, students should draw the driver pendulum, the responding pendulums of varying lengths, label the one at resonance as having maximum amplitude, and state clearly that resonance happens when driving frequency equals natural frequency. This qualitative description, rather than a numerical calculation, is the expected form of answer for most resonance questions.
How it is examined
Paper 1 questions often ask you to identify examples of damping or resonance from everyday situations, or to distinguish between external and internal damping using given scenarios. Paper 2 structured questions commonly present a diagram such as Barton's pendulums or a graph of amplitude against driving frequency, and use command words like "state" to identify the condition for resonance, "explain" to describe why amplitude decreases with damping or peaks at resonance, and "describe" to outline an everyday application or a way to reduce unwanted resonance, such as damping in bridges or vehicle suspension systems.
"Explain" answers need a chain of reasoning linking cause to effect, not just a restated definition. Paper 3 may involve a practical activity observing a damped oscillation, such as a mass-spring system with a card attached to increase air resistance, where students record how amplitude decreases with time.
A common mistake is confusing resonance with simply increasing the driving force, when in fact resonance specifically depends on matching the driving frequency to the natural frequency, not on the size of the force applied.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)