COMSATS NTS-based Test Physics (NAT-IE / NAT-IM / NAT-ICS) Syllabus

Define Simple Harmonic Motion (SHM).

SHM is the oscillatory motion in which the restoring force (or acceleration) is directly proportional to the displacement from the mean position and directed toward it: a = −ω²x.

Give the formula for the time period of a simple pendulum.

T = 2π√(L/g), where L is the length of the pendulum and g is the acceleration due to gravity. Period is independent of mass and amplitude.

Give the formula for the time period of a mass-spring system.

T = 2π√(m/k), where m is the mass and k is the spring constant (force constant).

In SHM, where are velocity and acceleration maximum and minimum?

Velocity is maximum at the mean position and zero at the extremes. Acceleration is maximum at the extremes and zero at the mean position.

Define amplitude, frequency, and time period of an oscillation.

Amplitude is the maximum displacement from the mean position. Frequency (f) is the number of oscillations per second (Hz). Time period (T) is the time for one complete oscillation; T = 1/f.

State the wave equation relating speed, frequency, and wavelength.

v = fλ, where v is wave speed, f is frequency, and λ is wavelength.

Distinguish between transverse and longitudinal waves with examples.

In transverse waves particles vibrate perpendicular to the direction of propagation (e.g., light, water waves). In longitudinal waves particles vibrate parallel to propagation (e.g., sound waves).

What is the principle of superposition of waves?

When two or more waves overlap, the resultant displacement at any point is the algebraic sum of the displacements of the individual waves.

Distinguish between constructive and destructive interference.

Constructive interference occurs when waves are in phase (path difference = nλ), giving maximum amplitude. Destructive interference occurs when waves are out of phase (path difference = (n+½)λ), giving minimum/zero amplitude.

What is a node and an antinode in a stationary wave?

A node is a point of zero displacement (no vibration); an antinode is a point of maximum displacement. Adjacent nodes are λ/2 apart.

What is the approximate speed of sound in air at room temperature, and how does it change with temperature?

About 340 m/s at 20°C. The speed of sound increases as temperature increases (approximately 0.6 m/s per °C rise).

In which medium does sound travel fastest: solid, liquid, or gas? Why?

Sound travels fastest in solids, then liquids, then gases, because solids have greater elasticity and tightly packed particles that transmit vibrations more efficiently. Sound cannot travel in a vacuum.

Define the Doppler effect.

The apparent change in the observed frequency of a wave due to relative motion between the source and the observer. Frequency increases as they approach and decreases as they recede.

What is the audible frequency range for the human ear, and define ultrasonic and infrasonic sound?

Audible range is 20 Hz to 20,000 Hz. Sound above 20,000 Hz is ultrasonic; below 20 Hz is infrasonic.

Distinguish between loudness, pitch, and quality (timbre) of sound.

Loudness depends on amplitude (intensity); pitch depends on frequency; quality (timbre) depends on the waveform/harmonics and distinguishes sounds of the same pitch and loudness.

Give the formula to convert Celsius to Kelvin and to Fahrenheit.

K = °C + 273.15; °F = (9/5)°C + 32.

State the three modes of heat transfer and define each briefly.

Conduction: heat transfer through a material by particle collisions without bulk movement. Convection: heat transfer by the movement of fluid (currents). Radiation: heat transfer by electromagnetic waves, requiring no medium.

Define specific heat capacity and give its formula.

Specific heat capacity is the heat required to raise the temperature of 1 kg of a substance by 1 K (or 1°C). Q = mcΔT, where c is specific heat. SI unit: J/(kg·K).

Define latent heat of fusion and latent heat of vaporization.

Latent heat of fusion is the heat needed to change 1 kg of a solid to liquid at constant temperature. Latent heat of vaporization is the heat needed to change 1 kg of liquid to gas at constant temperature. Q = mL.

What is thermal equilibrium (basis of the Zeroth Law of Thermodynamics)?

Two bodies are in thermal equilibrium when they are at the same temperature, with no net heat flow between them. The Zeroth Law states that if A is in equilibrium with C and B with C, then A and B are in equilibrium.

State the First Law of Thermodynamics and give its formula.

Energy is conserved: the heat added to a system equals the change in internal energy plus the work done by the system. ΔQ = ΔU + ΔW.

State the Second Law of Thermodynamics.

Heat cannot spontaneously flow from a colder body to a hotter body; some heat must always be rejected. No heat engine can be 100% efficient (entropy of an isolated system tends to increase).

Give the formula for the efficiency of a heat engine.

Efficiency η = W/Q₁ = 1 − Q₂/Q₁, where Q₁ is heat absorbed from the hot reservoir and Q₂ is heat rejected to the cold reservoir.

Define an isothermal process and an adiabatic process.

Isothermal: a process at constant temperature (ΔU = 0, so ΔQ = ΔW). Adiabatic: a process with no heat exchange with surroundings (ΔQ = 0, so ΔU = −ΔW).

State the postulates of the kinetic theory of gases.

Gas consists of large numbers of tiny molecules in constant random motion; their volume is negligible compared with the container; collisions are perfectly elastic with no energy loss; there are no intermolecular forces; and average kinetic energy is proportional to absolute temperature.

State the ideal gas equation and Boyle's, Charles's, and Pressure (Gay-Lussac's) laws.

Ideal gas: PV = nRT. Boyle's law: PV = constant at constant T. Charles's law: V/T = constant at constant P. Gay-Lussac's law: P/T = constant at constant V.

How is the average kinetic energy of a gas molecule related to temperature?

Average translational KE = (3/2)kT, where k is Boltzmann's constant and T is the absolute (Kelvin) temperature. KE is directly proportional to absolute temperature.

State Coulomb's law and give its formula.

The force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them: F = kq₁q₂/r², where k = 9×10⁹ N·m²/C².

Define electric field intensity and give its formula and unit.

Electric field intensity is the force per unit positive charge at a point: E = F/q. Unit is N/C or V/m. For a point charge, E = kq/r².

Define capacitance and give its formula and SI unit.

Capacitance is the ability to store charge per unit potential difference: C = Q/V. SI unit is the farad (F) = C/V.

State Ohm's law and give its formula. What is the SI unit of resistance?

At constant temperature, the current through a conductor is directly proportional to the voltage across it: V = IR. The SI unit of resistance is the ohm (Ω).