Comprehensive Exam Review – Matter, Energy, Waves, Electricity & Magnetism

Collisions and Energy Conversion

• Inelastic Collision
  • Definition: A collision in which the total kinetic energy before and after impact is not the same (some kinetic energy is converted to other energy forms such as heat, sound, deformation).
  • Key idea: Energy is transformed, not lost; the law of conservation of energy still applies, but kinetic → other forms.
  • Example you could cite on an exam:
  • A lump of clay thrown against a wall and sticking to it.
  • Car crash in which metal deforms and heats.

Kinetic-Molecular Theory & Properties of Matter

• All matter is composed of constantly moving particles.
• Evidence for particle motion:
  • Brownian motion: random jiggling of tiny particles in a fluid.
  • Gas laws (quantitative support).

The Three Fundamental Gas Laws (state each, variables held constant, relationship)

• Boyle’s Law
  • Statement: For a fixed mass of gas at constant temperature, $P \propto \dfrac{1}{V}$.
  • Constant: Temperature.
  • Relationship: Inverse (pressure ↑, volume ↓ and vice-versa).
• Charles’ Law
  • Statement: For a fixed mass of gas at constant pressure, $V \propto T$ (with $T$ in kelvin).
  • Constant: Pressure.
  • Relationship: Direct (temperature ↑, volume ↑).
• Gay-Lussac’s Law
  • Statement: For a fixed mass of gas at constant volume, $P \propto T$.
  • Constant: Volume.
  • Relationship: Direct (temperature ↑, pressure ↑).

Energy & Thermodynamics

• Temperature vs. Heat
  • Temperature: Measure of average kinetic energy of particles.
  • Heat: Energy transfer due to temperature difference (flows high → low).
• Specific Heat Capacity (c)
  • Definition: Heat required to raise 1 kg of a substance by $1\,^{\circ}!\text{C}$.
  • Exam expectation: Compare two materials with different $c$ values.
  • Example: Water (high c \approx 4186\,\text{J·kg}^{-1}\text{·K}^{-1}) vs. Sand (low c \approx 830\,\text{J·kg}^{-1}\text{·K}^{-1}). If equal heat added, water’s temperature rises much less.
• First Law of Thermodynamics
  • Energy cannot be created/destroyed; can change form. In heat processes, $\Delta U = Q - W$ (internal energy change = heat in – work out).
• Second Law of Thermodynamics
  • Heat spontaneously flows from hot → cold; processes have a preferred direction (increasing entropy).

Kinetic vs. Potential Energy

• Kinetic Energy (KE): Energy of motion.
  • Example formula: $KE = \dfrac{1}{2}mv^{2}$.
• Potential Energy (PE): Energy of position or stored energy.
  • Gravitational PE: $PE = mgh$.
• Conversion illustration (falling object):
  • Top of building ⇒ maximum $PE$, zero $KE$.
  • During fall ⇒ $PE \downarrow$ converts to $KE \uparrow$.
  • Sum $PE + KE$ remains constant (neglecting air resistance).

Waves: Core Terminology & Quantities

• Amplitude (A): Maximum displacement; indicates wave energy.
• Wavelength (\lambda):
  • Transverse: crest-to-crest distance.
  • Longitudinal: compression-to-compression.
• Frequency (f): Number of waves passing a point per unit time (Hz).
• Period (T): Time for one cycle. Reciprocal to frequency:
  • $f = \dfrac{1}{T} \quad \text{or} \quad T = \dfrac{1}{f}$.
• Velocity (v): Wave travel distance per unit time; governed by
  • $v = f\lambda$.

Types of Waves

• Transverse: Particle vibration ⟂ wave direction.
• Longitudinal: Particle vibration ∥ wave direction (e.g., sound).

Energy Transformations in Ultrasound Imaging (know all FOUR)

1. Electrical energy (from system) →
2. Mechanical (acoustic) energy in transducer crystal.
3. Acoustic wave enters body → part returns as mechanical echo.
4. Transducer reconverts mechanical echo → electrical signal for image.

Wave-Matter Interactions

• Reflection: Bounce from a boundary.
• Refraction: Bending due to speed change between media.
  • You will label these on a diagram.

Speed of Sound Factors

• Material properties:
  • Elasticity (bulk modulus) ↑ ⇒ speed ↑.
  • Density ↑ ⇒ speed ↓ (if elasticity unchanged).
• Environmental modifiers:
  • Temperature ↑ ⇒ speed ↑ (air).
  • Humidity ↑ ⇒ speed ↑ (moist air lighter).

Two-Way (Echo) Travel Calculations

• Common “distance = rate × time” with doubling for out-and-back path.
  • $d = \dfrac{v t}{2}$ when $t$ is total echo time.
  • Show all algebraic steps on exam.

Doppler Effect

• Apparent frequency shift due to relative motion between source and observer.
• Practical application: Police radar, medical Doppler ultrasound, siren pitch change.

Electricity & Magnetism Essentials

• Static Electricity (Polarization)
  • Charge separation within an object → net attractions/repulsions without conduction.
• Electric Field (E-field)
  • Region surrounding a charge where an electric force is exerted.
• Magnetic Field (B-field)
  • Region energized by magnetic poles; shows force on other magnets or moving charges.
• Predicting Charge Movement
  • Use electric field lines (point from + to –); charges follow field direction (positive) or opposite (negative).
• Right-Hand Rule (current → field)
  • Thumb: conventional current (I) direction.
  • Curled fingers: encircling magnetic field direction.
  • Be prepared to describe in words and draw arrows.

Practical/Philosophical Points & Study Tips

• Always relate examples to real-world phenomena (e.g., temperature vs. heat when cooking; Doppler in weather radar).
• Show respect for energy conservation: even when kinetic seems “lost,” it re-emerges as sound, thermal, deformation, etc.
• Connect gas-law demos to everyday life (e.g., aerosol can cooling when sprayed ⇒ Joule-Thomson expansion).
• For calculations, clearly write knowns/unknowns, formula, substitution, and units.
• Diagram labeling (reflection/refraction, field lines) is an easy score—practice neat arrows.

Good luck on your final – mastery comes from practising problems, reciting definitions aloud, and teaching concepts to a peer.