School and DİM-level physics: questions and answers

Question 1

How can I learn physics from zero?

Accepted Answer

Start with mechanics and follow the order of your textbook, because each topic builds on the last: dynamics is hard to follow without kinematics, and energy is hard to follow without dynamics. In each topic, first understand what is physically happening, then see where the formula comes from, and solve a few problems every day, starting with the simplest. If fractions, equations, powers or basic trigonometry are shaky, work on them alongside, since physics problems are built on exactly that maths.

Question 2

How do I learn to solve physics problems?

Accepted Answer

Use the same routine every time: read the problem carefully, list the given data and convert it to SI units, draw a sketch, pick the law that describes what's happening, solve with letters first and plug in numbers only at the end. Then check the units and whether the answer is realistic: if a pedestrian comes out at 50 m/s, something has gone wrong. Worked examples help, but the real skill comes from finishing problems on your own. OrujovAI's Solve explains why each step is taken and then gives you a similar problem to practise.

Question 3

How do I prepare for DİM physics?

Accepted Answer

Start with the official physics exam programme on dim.gov.az and plan your topics around it. In the current model, physics is part of group I (both the RK and Rİ subgroups) with a weighting of 1.5 and of group IV with a weighting of 1, and in the block exam each subject has multiple-choice tasks, tasks with a coded answer and tasks with a written answer. Work topic by topic: theory, then plenty of problems on that topic, and a timed mixed test every week, including the past papers DİM itself publishes. Check the exam structure and rules against the current announcement on dim.gov.az each year.

Question 4

How can I memorize physics formulas?

Accepted Answer

Understanding beats cramming: once you know momentum is simply mass times velocity, you won't forget p = mv. Checking units also helps, because both sides of a correct formula have the same units. Make a one-page summary for each topic, put formulas on flashcards and review them at spaced intervals over several days, but using them in problems is what really makes them stick. Many formulas are quicker to derive than to remember: in one turn an object covers the circumference 2πr, so its speed in circular motion is v = 2πr/T.

Question 5

Can AI teach me physics?

Accepted Answer

Yes, and physics suits it well, because the hard part is usually picturing what's happening rather than the formula itself. Ask the AI to explain the situation with an everyday example, list every force acting on the object and test you with questions like “what changes if the mass doubles?”. It can slip on arithmetic, signs and units, so check results against your textbook. OrujovAI's Live Tutor teaches a lesson out loud with slides, writes the working on a board and pauses for short checks, and its free physics example lessons can be watched without an account.

Question 6

What is kinematics?

Accepted Answer

Kinematics is the part of mechanics that describes motion without asking what causes it: where an object is, how fast it is moving and how its velocity changes. Its key quantities are position, displacement, distance, velocity, acceleration and time. Why an object moves the way it does, meaning the forces involved, is the subject of the next topic, dynamics.

Question 7

What is uniform motion?

Accepted Answer

In uniform straight-line motion, an object covers equal distances in equal time intervals, so its velocity stays constant in both size and direction. Distance is s = vt and position is x = x₀ + vt. On a graph, velocity against time is a horizontal line, while position against time is a straight sloping line.

Question 8

How do I find distance in uniformly accelerated motion?

Accepted Answer

The main formula is s = v₀t + at²/2, where v₀ is the initial velocity, a the acceleration and t the time; when an object slows down, the acceleration points against the velocity and is taken as negative. If the time isn't given, use v² = v₀² + 2as, and if both velocities and the time are known, s = (v₀ + v)t/2. All of these come from the area under the velocity–time graph, so sketching it often does half the work.

Question 9

What is free fall?

Accepted Answer

Free fall is motion under gravity alone, ignoring air resistance. In free fall, all objects accelerate at the same rate regardless of their mass, g ≈ 9.8 m/s², which problems often round to 10 m/s². For an object dropped from rest, h = gt²/2 and v = gt, and an object thrown straight up reaches a maximum height of h = v₀²/2g.

Question 10

How do I calculate the motion of a horizontally thrown object?

Accepted Answer

Split the motion in two: horizontally the object moves at a constant v₀, and vertically it falls freely. The time of flight depends only on the height, t = √(2h/g), and the horizontal range is l = v₀t. At any moment the horizontal velocity is v₀ and the vertical velocity is gt, and the overall speed comes from Pythagoras' theorem. In OrujovAI's Solve you can work through a problem like this step by step, with a graph where it helps.

Question 11

What is circular motion?

Accepted Answer

Even at constant speed, an object moving in a circle keeps changing direction, so it has an acceleration pointing to the centre, the centripetal acceleration a = v²/r. The motion is described by the period T (the time for one full turn), the frequency f = 1/T and the angular velocity ω = 2π/T, with linear speed v = 2πr/T = ωr. The force that provides this acceleration, such as string tension, friction or gravity, always points towards the centre.

Question 12

What is Newton's first law?

Accepted Answer

The first law, or law of inertia, says that if no force acts on an object, or the forces on it cancel out, the object stays at rest or keeps moving in a straight line at constant speed. It holds in inertial frames of reference. Passengers lurching forward when a bus brakes hard are an everyday example of inertia. All three laws are the topic of one of Live Tutor's free example lessons, taught in Azerbaijani.

Question 13

What is Newton's second law?

Accepted Answer

An object's acceleration is directly proportional to the net force on it and inversely proportional to its mass: a = F/m, or F = ma. The acceleration always points in the direction of the net force; force is measured in newtons (N), mass in kilograms and acceleration in m/s². In problems, draw every force on a free-body diagram, choose axes and write the law separately for each axis.

Question 14

What is Newton's third law?

Accepted Answer

When two objects interact, they exert forces on each other that are equal in size and opposite in direction: F₁₂ = −F₂₁. These forces act on different objects, so they never cancel each other out. Push on a wall and the wall pushes back on you just as hard; a rocket moves forward because it pushes exhaust gas backwards.

Question 15

How do I calculate friction force?

Accepted Answer

Sliding (kinetic) friction is F = μN, where μ is the coefficient of friction and N is the normal force. On a horizontal surface with no other vertical forces, N = mg; on a slope at angle α, N = mg cos α. If the object isn't moving, static friction simply matches the applied force up to a maximum of μN, so writing F = μN automatically is a common mistake.

Question 16

What is the law of universal gravitation?

Accepted Answer

Newton's law says any two masses attract each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them: F = Gm₁m₂/r². Here G ≈ 6.67 × 10⁻¹¹ N m²/kg² is the gravitational constant. The law explains the orbits of planets and satellites, and near the Earth's surface it shows up as weight, mg.

Question 17

What is momentum?

Accepted Answer

Momentum is a vector quantity equal to mass times velocity: p = mv, measured in kg m/s, and it points the same way as the velocity. The impulse of a force, FΔt, equals the change in momentum: FΔt = Δp. That's why stretching out the time of an impact, as an airbag does, reduces the force.

Question 18

What is the law of conservation of momentum?

Accepted Answer

In a closed system, where no external forces act or they cancel out, the total momentum stays the same: m₁v₁ + m₂v₂ = m₁v₁′ + m₂v₂′, added as vectors. Collisions, explosions and the recoil of a gun are all calculated with it. Before solving, choose a positive direction and give velocities pointing the other way a minus sign.

Question 19

How do I calculate work and power?

Accepted Answer

The work done by a constant force is W = Fs cos θ, where θ is the angle between the force and the displacement; work is measured in joules (J). A force perpendicular to the motion does no work, and one acting against the motion, like friction, does negative work. Power is the rate of doing work, P = W/t, measured in watts (W), and at constant velocity P = Fv.

Question 20

What are kinetic and potential energy?

Accepted Answer

Kinetic energy is the energy of motion: Ek = mv²/2. Potential energy depends on position: for an object raised to height h above the ground, Ep = mgh, and for a stretched or compressed spring, Ep = kx²/2. Both are measured in joules, and the value of potential energy depends on where you choose the zero level.

Question 21

What is the law of conservation of energy?

Accepted Answer

Energy is never created or destroyed; it only changes from one form to another or passes from one object to another. In mechanics this means that in a closed system without friction or air resistance, the total mechanical energy Ek + Ep stays constant: an object dropped from height h, for example, hits the ground at v = √(2gh). With friction, part of the mechanical energy turns into heat, and that loss equals the work done by friction.

Question 22

What is pressure and how do I calculate it?

Accepted Answer

Pressure is the force acting perpendicular to a surface divided by its area: p = F/A, measured in pascals (1 Pa = 1 N/m²). The same force on a smaller area gives more pressure, which is why a sharp knife cuts better than a blunt one. The pressure of a liquid column is p = ρgh and doesn't depend on the shape of the container; normal atmospheric pressure is about 101 kPa, or 760 mmHg.

Question 23

What is the buoyant (Archimedes) force?

Accepted Answer

An object in a liquid or gas feels an upward push called the buoyant force: F = ρgV, where ρ is the density of the fluid and V is the volume of the submerged part. It depends on the weight of the fluid the object displaces, not on the object's own density. If the object is less dense than the fluid it floats, if it's denser it sinks, and for a floating object the buoyant force equals its weight.

Question 24

What is Pascal's law?

Accepted Answer

Pascal's law says that pressure applied to an enclosed liquid or gas is transmitted undiminished to every point and in every direction. Hydraulic presses and car brakes work this way: a force on a small piston becomes larger on a big piston in proportion to their areas, F₂/F₁ = A₂/A₁. The gain in force is paid for with an equal loss in distance, so the work done doesn't increase.

Question 25

What are the gas laws?

Accepted Answer

For a fixed mass of ideal gas there are three laws: Boyle's law at constant temperature (pV = constant), Charles's law at constant pressure (V/T = constant) and Gay-Lussac's pressure law at constant volume (p/T = constant). They combine into the ideal gas equation pV = nRT, where n is the amount in moles and R ≈ 8.31 J/(mol K). Temperatures in these formulas must always be in kelvin: T = t + 273. Note that Azerbaijani and Russian textbooks swap two of the names, calling the constant-pressure law Gay-Lussac's and the constant-volume law Charles's.

Question 26

What is the first law of thermodynamics?

Accepted Answer

It is conservation of energy applied to heat: the heat supplied to a system goes into changing its internal energy and into the work the gas does on its surroundings, Q = ΔU + W. In an isothermal process ΔU = 0, in an isochoric (constant-volume) process W = 0, and in an adiabatic process Q = 0. Watch the sign convention: some textbooks write the law with the work done on the gas, ΔU = Q + W.

Question 27

How do I calculate the amount of heat?

Accepted Answer

For heating or cooling, use Q = mcΔT, where c is the specific heat capacity (about 4200 J/(kg °C) for water). During a change of state the temperature stays constant and Q = mL, where L is the specific latent heat of fusion for melting or of vaporization for boiling, while burning fuel releases Q = qm. For mixing problems, write a heat balance: the heat given off by the hot object equals the heat taken in by the cold one.

Question 28

What is electric charge?

Accepted Answer

Electric charge is the property that makes objects take part in electromagnetic interactions, measured in coulombs (C). There are two kinds: like charges repel and unlike charges attract. Every charge is a whole-number multiple of the elementary charge, e ≈ 1.6 × 10⁻¹⁹ C, and in a closed system the total charge is conserved.

Question 29

What is Coulomb's law?

Accepted Answer

The force between two point charges is proportional to the product of their magnitudes and inversely proportional to the square of the distance between them: F = k|q₁||q₂|/r², with k ≈ 9 × 10⁹ N m²/C² in a vacuum. The force acts along the line joining the charges. In a medium it is weaker by a factor of ε, the medium's relative permittivity.

Question 30

What is Ohm's law?

Accepted Answer

Ohm's law for part of a circuit says the current is directly proportional to the voltage and inversely proportional to the resistance: I = V/R, with current in amperes, voltage in volts and resistance in ohms. For a complete circuit you also include the source's internal resistance: I = ε/(R + r), where ε is the emf. You can also watch Live Tutor's free lesson “Ohm's law and electric circuits”, taught in Azerbaijani, with no account needed.

Question 31

What are series and parallel circuits?

Accepted Answer

In a series circuit the components are connected one after another: the current is the same through all of them, the voltages add up and the total resistance is R = R₁ + R₂. In a parallel circuit they are connected across the same two points: the voltage across each is the same, the currents add up and the total resistance comes from 1/R = 1/R₁ + 1/R₂, which is always smaller than the smallest resistor. Household appliances are wired in parallel, which is why switching one off doesn't turn off the rest.

Question 32

How do I calculate the work and power of electric current?

Accepted Answer

The work done by a current is W = VIt and the power is P = VI; using Ohm's law, power can also be written as P = I²R or P = V²/R. The heat released in a conductor follows Joule's law, Q = I²Rt. Household energy is measured in kilowatt-hours, 1 kWh = 3.6 × 10⁶ J, which is what your electricity meter counts.

Question 33

What is a capacitor?

Accepted Answer

A capacitor stores electric charge and energy: it is two conducting plates separated by an insulator (dielectric). Its capacitance is C = Q/V, or C = εε₀A/d for a parallel-plate capacitor, measured in farads (F). A charged capacitor stores energy W = CV²/2; in series 1/C = 1/C₁ + 1/C₂ and in parallel C = C₁ + C₂, the opposite of resistors.

Question 34

What is a magnetic field?

Accepted Answer

A magnetic field surrounds moving charges, current-carrying wires and magnets, and it acts only on moving charges. Its main measure is the magnetic flux density (also called magnetic induction) B, measured in teslas (T). It is drawn with field lines that, outside a magnet, leave the north pole and enter the south pole, and the direction of the field around a straight current is found with the right-hand grip rule.

Question 35

What are the Ampère force and the Lorentz force?

Accepted Answer

The Ampère force is the force a magnetic field exerts on a current-carrying wire: F = BIl sin α, where l is the length of wire in the field and α the angle between the current and B. The Lorentz force is the force on a single moving charged particle: F = |q|vB sin α. The directions of both are found with the left-hand rule; because the Lorentz force is perpendicular to the velocity, it does no work, and a particle entering a uniform field at right angles to the field lines is bent into a circle.

Question 36

What is electromagnetic induction?

Accepted Answer

Electromagnetic induction is the creation of a current in a closed loop when the magnetic flux through it changes; Faraday discovered it in 1831. The induced emf equals the rate of change of flux, ε = −ΔΦ/Δt, where Φ = BA cos α. The minus sign expresses Lenz's law: the induced current opposes the change in flux that caused it. Generators and transformers work on this principle.

Question 37

What are mechanical oscillations?

Accepted Answer

Mechanical oscillations are motions that repeat at regular intervals around an equilibrium position, like a swing or a mass on a spring. They are described by the amplitude (the largest displacement), the period T and the frequency f = 1/T, measured in hertz (Hz). A mass on a spring has a period of T = 2π√(m/k), and during the oscillation energy keeps changing between kinetic and potential.

Question 38

How do I find the period of a simple pendulum?

Accepted Answer

For small swings, the period of a simple pendulum is T = 2π√(l/g), where l is the length of the string and g the acceleration due to gravity. It doesn't depend on the mass of the bob or on the amplitude, as long as the swings are small: make the string 4 times longer and the period doubles. On the Moon, where g is smaller, the same pendulum would swing more slowly.

Question 39

What is a wave and how do I find the wavelength?

Accepted Answer

A wave is an oscillation travelling through a medium or a field, carrying energy rather than matter. The wavelength λ is the distance the wave travels in one period: λ = vT = v/f, where v is the wave speed and f the frequency. If the particles oscillate across the direction of travel the wave is transverse, and if they oscillate along it the wave is longitudinal.

Question 40

How does sound travel?

Accepted Answer

Sound is a longitudinal mechanical wave, so it needs a medium (a gas, liquid or solid) and cannot travel through a vacuum. In air at room temperature it moves at about 340 m/s, in water at about 1500 m/s and in steel at over 5000 m/s. People hear frequencies from roughly 20 Hz to 20,000 Hz; pitch depends on frequency and loudness on amplitude.

Question 41

What is refraction of light?

Accepted Answer

Refraction is the change in direction of light as it crosses from one medium into another, because light travels at different speeds in different media. Snell's law states n₁ sin θ₁ = n₂ sin θ₂, where n = c/v is the refractive index of each medium. When light passes from a denser medium into a less dense one at an angle larger than the critical angle, total internal reflection happens, which is how optical fibres carry light.

Question 42

How do lenses work?

Accepted Answer

A lens bends light by refraction: a convex (converging) lens, thicker in the middle, brings parallel rays together at the focal point, while a concave (diverging) lens spreads them out. The thin-lens equation 1/f = 1/u + 1/v links the object distance u, the image distance v and the focal length f, with signs set by your textbook's convention (a diverging lens has a negative focal length). Whether the image is bigger or smaller, upright or inverted, real or virtual depends on where the object sits relative to the focal point.

Question 43

How do I calculate the optical power of a lens?

Accepted Answer

Optical power is the reciprocal of the focal length: P = 1/f, with f in metres, giving an answer in dioptres (D). A lens with a focal length of 25 cm, for example, has a power of 1/0.25 = 4 D. Converging lenses have positive power and diverging lenses negative, and the powers of thin lenses placed close together add up.

Question 44

What is the photoelectric effect?

Accepted Answer

The photoelectric effect is the emission of electrons from a material, usually a metal surface, when light shines on it. Einstein's equation says the photon's energy goes into the work function plus the electron's kinetic energy: hf = φ + mv²/2. Electrons are emitted only if the light's frequency is above the threshold frequency f₀ = φ/h; the maximum kinetic energy of the electrons depends on the frequency, and their number depends on the light's intensity.

Question 45

What is the structure of an atom?

Accepted Answer

An atom has a tiny, positively charged nucleus at its centre that holds almost all of its mass, with electrons moving around it. The nucleus is made of protons and neutrons: the number of protons Z is the atomic number, and the mass number is A = Z + N. A neutral atom has as many electrons as protons; Rutherford proposed the nuclear model, and Bohr postulated that electrons can only occupy certain energy levels.

Question 46

What is radioactivity?

Accepted Answer

Radioactivity is the spontaneous decay of unstable atomic nuclei, giving off radiation; Becquerel discovered it in 1896. The three main types are alpha (helium nuclei), beta (fast electrons) and gamma (high-energy electromagnetic radiation). The half-life T is the time it takes for half of the nuclei to decay, and the number left after a time t is N = N₀/2^(t/T).

Question 47

How do I write nuclear reactions?

Accepted Answer

Write the mass number at the top left of each symbol and the charge (atomic) number at the bottom left; both totals must be equal on the two sides of the reaction. For example, the first artificial nuclear transmutation, carried out by Rutherford in 1919, is written ¹⁴₇N + ⁴₂He → ¹⁷₈O + ¹₁H. To find an unknown particle, balance the mass and charge numbers; an alpha particle is written ⁴₂He, a neutron ¹₀n, a proton ¹₁H and an electron ⁰₋₁e.

Question 48

How do I convert units to SI?

Accepted Answer

The SI base units are the metre, kilogram, second, ampere, kelvin, mole and candela, so convert all the given data into them before solving. The conversions you'll need most: divide km/h by 3.6 to get m/s (72 km/h = 20 m/s), 1 cm = 0.01 m, 1 cm² = 10⁻⁴ m², 1 L = 10⁻³ m³ and 1 g/cm³ = 1000 kg/m³. Learn the prefixes too: kilo 10³, mega 10⁶, milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹.

Question 49

How should I write the “given” data in a physics problem?

Accepted Answer

Under the heading “Given”, list each quantity with its symbol, value and unit, for example m = 2 kg and v = 36 km/h, and next to it the value converted to SI (10 m/s). Below that, write “Find” with the quantity you need, and set out the solution to the right or underneath. Watch for hidden data: “starts from rest” means v₀ = 0 and “comes to a stop” means the final velocity is zero, so add those to the list as well.

Question 50

Where can I find DİM-format physics tests?

Accepted Answer

For official tasks, go to DİM: after each exam the tasks used are published with the correct answers on dim.gov.az, and DİM's test collections and Abituriyent journal are sold on abiturient.az. OrujovAI's exam practice builds short DİM-format tests in 8 subjects, physics included, at three difficulty levels, explains every question and shows your weak topics from the results. It has no coded-answer or written tasks, so practise those with DİM's own material.

Question 51

Can AI check my physics solution?

Accepted Answer

Yes: send a photo or the text of your solution and ask the AI to find the faulty step rather than just give the answer. A request that works well is: “Don't tell me the answer, show me where I went wrong and explain why.” AI can be wrong too, so check what it says yourself: do the units work out, and does the result make physical sense? In OrujovAI's chat you can upload a photo of your work and go through it step by step.

Question 52

How do I calculate measurement error in a physics lab?

Accepted Answer

For a single reading, the instrument's uncertainty is usually taken as half the smallest scale division. If you take several readings, find the mean; the absolute error Δx is the average of the absolute deviations of the readings from the mean, and the relative (percentage) error is Δx divided by the mean, times 100%. Write the result as mean ± Δx with its unit, for example l = (12.4 ± 0.1) cm, and if your teacher or textbook uses a different method, follow that one.

Question 53

How is physics connected to everyday life?

Accepted Answer

For every new law, find an example around you: slipping on ice is low friction, a spoon that looks “broken” in a glass of tea is refraction, and droplets forming on a cold glass are condensation. Your electricity meter counts kilowatt-hours, a vacuum flask shows how heat transfer is stopped, and bicycle gears show how machines trade force for distance. Noting observations like these makes topics easier to remember and problem situations easier to picture.

Question 54

How do I prepare for a physics olympiad?

Accepted Answer

Olympiad problems go deeper than the syllabus and need stronger maths, so make the school material solid first and then move on to past olympiad problems. Don't jump to the solution on a hard problem: think it through on your own for a good while, and if you're still stuck take a small hint for the next step only; once you've seen a solution, try to reach the answer another way. In Azerbaijan the Republic subject olympiad is for grades 8 to 11: after the school and district (city) stages come the semifinal and final of the republic stage, and this year's dates and rules are published on edu.gov.az. Prepare for experimental rounds with simple measurement experiments at home.

Question 55

What are vector quantities in physics?

Accepted Answer

A vector quantity has both a size (magnitude) and a direction: displacement, velocity, acceleration, force, momentum, electric field strength and magnetic flux density are all vectors. Quantities with only a size, such as mass, time, distance, energy and temperature, are scalars. Vectors don't add like ordinary numbers but by the parallelogram or triangle rule: two perpendicular forces of 3 N and 4 N give a resultant of 5 N, not 7 N.

Question 56

How do I solve physics graph problems?

Accepted Answer

Start with the axes: which quantities, which units and what scale, because most mistakes come from misreading an axis. Then think about what the slope and the area under the graph mean: the slope of a position–time graph is velocity, the slope of a velocity–time graph is acceleration, and the area under a velocity–time graph is displacement. Read off specific points, such as where lines cross the axes or each other, and check them with a formula. Ask OrujovAI's chat to plot a relation such as v(t) = 10 − 2t, and you'll see the acceleration of −2 m/s² in the slope of the line and the displacement in the triangle under it.