Title: Physics Essentials — LearnCoachAssist

Q: What is physics?
A: Physics is the fundamental natural science that studies matter, its fundamental constituents, motion and behavior through space and time, and related entities like energy and force.

Q: What are the base SI units?
A: The base SI units are the metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.

Q: Distinguish between scalar and vector quantities.
A: Scalar quantities have only magnitude, such as mass or speed, while vector quantities have both magnitude and direction, such as velocity or force. Vectors are represented by arrows indicating direction and length for magnitude.

Q: What is the difference between distance and displacement?
A: Distance is the total path length traveled, a scalar, while displacement is the straight-line vector from initial to final position. Displacement can be zero even if distance is not, as in a closed loop.

Q: Define speed and velocity.
A: Speed is the scalar rate of change of distance with time, while velocity is the vector rate of change of displacement with time. Average speed is total distance over time; average velocity is displacement over time.

Q: What is acceleration?
A: Acceleration is the rate of change of velocity with time, a vector quantity. It can be positive, negative (deceleration), or change direction, calculated as a = Δv / Δt.

Q: State the three equations of motion for constant acceleration.
A: The equations are: v = u + at, s = ut + (1/2)at², and v² = u² + 2as, where u is initial velocity, v final velocity, a acceleration, s displacement, t time.

Q: What is Newton's First Law of Motion?
A: Newton's First Law states that an object at rest stays at rest and an object in motion stays in motion with constant velocity unless acted upon by a net external force. This describes inertia.

Q: Explain Newton's Second Law.
A: Newton's Second Law states that the net force on an object equals its mass times acceleration: F_net = ma. Acceleration is directly proportional to force and inversely to mass.

Q: What is Newton's Third Law?
A: Newton's Third Law states that for every action, there is an equal and opposite reaction. Forces come in pairs acting on different objects.

Q: Distinguish between mass and weight.
A: Mass is the amount of matter in an object, measured in kg, invariant. Weight is the gravitational force on mass, W = mg, varying with location.

Q: What is friction?
A: Friction is the force opposing relative motion between surfaces in contact. Static friction prevents motion; kinetic friction acts during sliding, both proportional to normal force.

Q: State the universal law of gravitation.
A: Newton's law of universal gravitation: Every particle attracts every other with force F = G m1 m2 / r², where G is the gravitational constant, directed along the line joining centers.

Q: Define work in physics.
A: Work is the product of force and displacement in the direction of force: W = F d cosθ. It is scalar, measured in joules (J).

Q: What is power?
A: Power is the rate of doing work or transferring energy: P = W / t or P = F v. Measured in watts (W), where 1 W = 1 J/s.

Q: What is kinetic energy?
A: Kinetic energy is energy of motion: KE = (1/2) m v². It depends on mass and speed squared.

Q: Define gravitational potential energy.
A: Gravitational potential energy is PE = m g h, energy due to position in a gravitational field. h is height above reference level.

Q: State the principle of conservation of mechanical energy.
A: In the absence of non-conservative forces like friction, total mechanical energy (KE + PE) is conserved. Energy converts between forms but sum remains constant.

Q: What is linear momentum?
A: Linear momentum is mass times velocity: p = m v, a vector quantity. Change in momentum relates to impulse.

Q: State the conservation of momentum.
A: In a closed system with no external forces, total momentum is conserved. Useful for collisions.

Q: Describe uniform circular motion.
A: In uniform circular motion, speed is constant but velocity changes direction, requiring centripetal acceleration a_c = v² / r towards center, provided by centripetal force.

Q: What is torque?
A: Torque is the rotational equivalent of force: τ = r F sinθ, causing angular acceleration. Measured in N·m.

Q: Define moment of inertia.
A: Moment of inertia (I) is the mass distribution resistance to rotational acceleration about an axis: I = Σ m r² for point masses.

Q: What is angular momentum?
A: Angular momentum is L = I ω or L = r × p, conserved in systems with no external torques.

Q: What is pressure in fluids?
A: Pressure is force per unit area: P = F / A. In fluids, it acts equally in all directions.

Q: State Archimedes' principle.
A: Archimedes' principle: Buoyant force equals weight of displaced fluid. Objects float if buoyant force ≥ weight.

Q: What are the Celsius and Kelvin temperature scales?
A: Celsius (°C) sets water freezing at 0°C and boiling at 100°C. Kelvin (K) is absolute: T(K) = T(°C) + 273.15, zero at absolute zero.

Q: Define specific heat capacity.
A: Specific heat capacity (c) is heat energy per unit mass per degree change: Q = m c ΔT. Varies by material.

Q: State the First Law of Thermodynamics.
A: The First Law states energy conservation: ΔU = Q - W, change in internal energy equals heat added minus work done by system.

Q: What is the Zeroth Law of Thermodynamics?
A: The Zeroth Law: If two systems are in thermal equilibrium with a third, they are in equilibrium with each other, defining temperature.

Q: What is a wave?
A: A wave is a disturbance propagating through space and time, carrying energy without net matter transport. Described by wavelength, frequency, speed.

Q: Distinguish transverse and longitudinal waves.
A: Transverse waves have oscillations perpendicular to propagation (e.g., light); longitudinal have parallel (e.g., sound). Both obey v = f λ.

Q: What is the speed of sound?
A: Speed of sound in ideal gas is v = √(γ P / ρ) or v = √(γ R T / M), about 343 m/s in air at 20°C.

Q: What is the Doppler effect?
A: Doppler effect: Observed frequency shifts due to relative motion between source and observer. f' = f (v ± vo) / (v ± vs).

Q: What is reflection of light?
A: Reflection: Angle of incidence equals angle of reflection. Law holds for mirrors.

Q: Define refraction.
A: Refraction: Bending of light at interface due to speed change. Snell's law: n1 sinθ1 = n2 sinθ2, n refractive index.

Q: What is a simple pendulum?
A: A simple pendulum approximates simple harmonic motion (SHM) for small angles, period T = 2π √(L / g) independent of mass.

Q: What is simple harmonic motion (SHM)?
A: SHM is oscillatory motion where restoring force proportional to displacement: F = -kx. Acceleration a = -ω² x, ω angular frequency.

Q: What is electric charge?
A: Electric charge is quantized property, positive (protons) or negative (electrons). Conserved, measured in coulombs (C).

Q: State Coulomb's law.
A: Coulomb's law: Force between charges F = k q1 q2 / r², k = 9×10^9 N·m²/C², attractive if opposite signs.

Q: What is an electric field?
A: Electric field E at point is force per unit positive charge: E = F / q. For point charge, E = k q / r² radial.

Q: Define electric potential.
A: Electric potential V is work per unit charge to bring from infinity: V = k q / r. Potential energy U = q V.

Q: What is electric current?
A: Electric current I is charge flow rate: I = ΔQ / Δt, measured in amperes (A). Conventional direction positive to negative.

Q: State Ohm's law.
A: Ohm's law: V = I R, voltage across resistor proportional to current, R resistance in ohms (Ω).

Q: Compare series and parallel circuits.
A: In series, current same, voltages add, total R = sum Ri. In parallel, voltage same, currents add, 1/R_total = sum 1/Ri.

Q: What is a magnetic field?
A: Magnetic field B exerts force on moving charges or magnets. Direction by right-hand rule; unit tesla (T).

Q: State Faraday's law of induction.
A: Faraday's law: Induced EMF = - dΦ_B / dt, where Φ_B magnetic flux. Basis of generators.

Q: What is special relativity?
A: Special relativity: Laws of physics same in inertial frames; speed of light c invariant. Leads to time dilation, length contraction.

Q: Explain time dilation.
A: Time dilation: Moving clock ticks slower: Δt = Δt0 / √(1 - v²/c²), Δt0 proper time.

Q: What is the photoelectric effect?
A: Photoelectric effect: Light ejects electrons from metal if frequency > threshold. Einstein: Energy E = h f, supports light quanta (photons).

Q: State the ideal gas law.
A: Ideal gas law: PV = n R T, relates pressure, volume, moles, temperature. R universal gas constant.

Q: What is entropy?
A: Entropy S measures disorder or unavailable energy. Second Law: ΔS_universe ≥ 0 for spontaneous processes.