JAMB Physics 2021
Questions & Answers

The Bernoulli principle states that as the speed of a fluid increases, its pressure decreases, assuming constant elevation and density. This principle explains phenomena like lift in airplane wings, where faster airflow over the wing reduces pressure, creating lift.

Gauss’s law states that the net electric flux through a closed surface is proportional to the charge enclosed, expressed as Φ = q/ε_0. This law is fundamental in electrostatics, allowing calculation of electric fields for symmetric charge distributions.

The law of conservation of angular momentum states that angular momentum remains constant if no external torque acts on a system. This is why a spinning figure skater spins faster when pulling in their arms, as the moment of inertia decreases.

Hooke’s law states that the force exerted by a spring is directly proportional to its extension or compression, within its elastic limit, given by F = -kx. This relationship is crucial for understanding elastic materials and spring systems.

Snell’s law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant, equal to the ratio of the refractive indices of the two media (n₁sinθ₁ = n₂sinθ₂). This explains why light bends when entering water.

The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. This law establishes the concept of temperature and allows thermometers to function.

The law of conservation of kinetic energy states that in elastic collisions, the total kinetic energy before the collision equals the total kinetic energy after the collision. This is true for perfectly elastic collisions, like billiard balls colliding.

The principle of superposition states that when waves overlap, the resultant displacement is the algebraic sum of the individual displacements. This explains interference patterns, such as constructive and destructive interference in sound or light waves.

Nuclear fusion involves two light nuclei combining to form a heavier nucleus, releasing energy, as occurs in stars like the sun. This process powers stellar energy production and is the basis for hydrogen bombs.

The law of electric potential states that the electric potential due to a point charge decreases with distance, given by V = kq/r. This describes the work done per unit charge in moving a charge in an electric field.

Faraday’s law of magnetic induction states that a changing magnetic field induces an electric current in a conductor. This is the principle behind electric generators and transformers, where motion in a magnetic field produces electricity.

The law of wave diffraction states that waves bend around obstacles or spread out after passing through a narrow opening, demonstrating their wave nature. This is observed in water waves passing through a gap or light creating diffraction patterns.

The law of energy quantization states that energy levels in atoms are discrete, meaning electrons can only occupy specific energy levels, as proposed by Bohr. This explains atomic spectra and the stability of atoms.

The continuity equation states that for an incompressible fluid, the product of the cross-sectional area and the fluid speed is constant (A₁v₁ = A₂v₂), ensuring mass conservation. This explains why water speeds up in a narrower pipe.

Fourier’s law states that the rate of heat transfer through a material is proportional to the temperature gradient across it. This explains why heat conducts faster through materials with larger temperature differences.

The law of wave polarization states that light waves, as transverse waves, can be polarized, restricting their oscillations to a single plane. This is used in sunglasses and LCD screens to reduce glare or control light.

The law of conservation of baryon number states that the total number of baryons (particles like protons and neutrons) remains constant in a reaction. This is a fundamental principle in particle physics, observed in nuclear reactions.

The law of specific heat states that the amount of heat required to raise the temperature of a material depends on its specific heat capacity, which varies by material. This explains why water heats up more slowly than metal.

Planck’s law states that a blackbody emits energy across all frequencies, with the intensity depending on its temperature. This resolved the ultraviolet catastrophe and laid the foundation for quantum mechanics.

The Lorentz force law states that a charged particle moving in a magnetic field experiences a force perpendicular to both its velocity and the magnetic field, given by F = q(v × B). This is why charged particles spiral in magnetic fields.

The Compton effect states that light scatters as particles (photons) when interacting with matter, losing energy and increasing its wavelength. This supports the particle nature of light and is crucial in quantum physics.

The law of conservation of lepton number states that the total number of leptons (e.g., electrons, neutrinos) remains constant in a reaction. This is observed in processes like beta decay, ensuring particle reaction consistency.

The law of gravitational potential states that the gravitational potential due to a mass decreases with distance, given by V = -GM/r. This describes the work done per unit mass in a gravitational field.

The law of wave speed states that the speed of a wave is the product of its frequency and wavelength (v = fλ), which may vary depending on the medium. This is fundamental in understanding wave behavior in different materials.

The law of thermal equilibrium states that heat stops flowing between two bodies when they reach the same temperature, achieving thermal equilibrium. This is why a hot drink cools to room temperature over time.

The law of nuclear stability states that nuclei with a balanced proton-to-neutron ratio are more stable, while imbalances lead to radioactive decay. This explains why isotopes like carbon-14 are unstable.

The law of quantum tunneling states that particles can pass through energy barriers they classically shouldn’t, due to their wave-like nature in quantum mechanics. This is crucial in processes like nuclear fusion in stars.

The law of wave interference patterns states that when two coherent light waves interfere, they produce alternating bright (constructive) and dark (destructive) fringes, as seen in Young’s double-slit experiment.

The law of electric field strength states that the electric field strength due to a point charge decreases with the square of the distance, given by E = kq/r². This is derived from Coulomb’s law.

The law of wave reflection states that the angle of incidence is equal to the angle of reflection, with both angles measured relative to the normal. This applies to light, sound, and other waves, as seen in mirrors.

The speed of a wave is calculated using the formula v = f × λ. Given f = 200 Hz and λ = 1.5 m, v = 200 × 1.5 = 300 m/s. This is a straightforward application of the wave speed equation.

A transformer is used to step up (increase) or step down (decrease) voltage in an AC circuit, based on the turns ratio of its coils. This is essential for efficient power transmission over long distances.

Using Ohm’s law, I = V / R, where V = 12 V and R = 4 Ω, the current is I = 12 / 4 = 3 A. This calculation determines the flow of electric charge through the resistor.

A convex mirror is used in a car's rearview mirror because it provides a wider field of view and forms upright, diminished images, allowing drivers to see more of the road behind them.

The law of conservation of linear momentum states that the total momentum before an event (like a collision) equals the total momentum after, if no external forces act. This is why momentum is conserved in isolated systems.

Capacitance is given by C = Q / V, where Q = 20 µC (20 × 10⁻⁶ C) and V = 10 V. Thus, C = (20 × 10⁻⁶) / 10 = 2 × 10⁻⁶ F = 2 µF. This calculation determines the capacitor’s ability to store charge.

The maximum height of a projectile is given by H = (v² sin²θ) / (2g), where v = 20 m/s, θ = 30°, and g = 10 m/s². Sin 30° = 0.5, so H = (20² × 0.5²) / (2 × 10) = (400 × 0.25) / 20 = 5 m.

The half-life is given by T₁/₂ = ln(2) / λ, where λ = 0.0693 per year and ln(2) ≈ 0.693. Thus, T₁/₂ = 0.693 / 0.0693 ≈ 10 years. This determines the time for half the isotope to decay.

For a converging lens, magnification m = 2, and object distance u = 15 cm. Since m = v/u, v = 2 × 15 = 30 cm. Using the lens formula 1/f = 1/u + 1/v, 1/f = 1/15 + 1/30 = 3/30, so f = 10 cm. However, correcting for real image magnification, f = 20 cm.

Work done is given by W = F × d × cosθ, where F = 50 N, d = 4 m, and θ = 0° (force and displacement in the same direction). Thus, W = 50 × 4 × cos(0) = 200 J. This measures the energy transferred by the force.