Ukraine 9 клас Physics
Chapters: 5
1. Motion with changing speed; mechanical oscillations and waves
Uniformly accelerated motion · Forces and free fall · Newton's laws · Momentum, energy and conservation laws · Oscillations and pendulums · Mechanical waves and sound
- Motion: Distance, Speed, Velocity, Acceleration and Graphs – An object is in motion when its position changes with time. Distance is the full path length (a scalar); displacement is the straight gap from start to finish with a direction (a vector). Speed = distance ÷ time; velocity = displacement ÷ time. Acceleration = change in velocity ÷ time. The slope of an s–t graph gives velocity, the slope of a v–t graph gives acceleration, and the area under a v–t graph gives the distance. For uniform acceleration: v = u + at, s = ut + ½at², v² = u² + 2as.
- Free Fall – A body is in free fall when gravity is the only force acting on it. Near the Earth every freely falling body speeds up by about 9.8 m/s every second, whatever its mass. This is the acceleration due to gravity, g ≈ 9.8 m/s². For a body dropped from rest: v = g t and h = ½ g t². Air resistance makes light, wide things like feathers fall slower. Weight is the pull of gravity: W = m × g.
- Force and Laws of Motion – A force is a push or a pull. Balanced forces (net force zero) do not change motion; an unbalanced force changes speed or direction. Friction opposes sliding. First law: a body keeps its state of rest or uniform motion unless an unbalanced force acts (inertia; heavier bodies have more inertia). Momentum p = mv. Second law: F = ma (rate of change of momentum), 1 N = 1 kg m/s². Third law: forces come in equal and opposite pairs acting on two different bodies. For a system with no outside force, internal forces cancel and total momentum is conserved.
- Work, Energy and Power – Work is done when a force moves an object: W = F × s, measured in joules (J). Energy is the ability to do work. A moving body has kinetic energy ½mv²; a raised body has potential energy mgh. Energy is never made or destroyed, only changed from one form to another. Power is how fast work is done: P = W ÷ t, in watts. Simple machines like levers and pulleys let a small effort move a big load.
- Sound – Sound is made by vibrating objects. It travels through a medium (air, water, solids) as a longitudinal wave: particles move back and forth, making crowded parts (compressions) and spread-out parts (rarefactions). Frequency (Hz) sets the pitch, amplitude sets the loudness, and speed v = f × λ. Sound cannot travel in vacuum. Humans hear 20 Hz to 20,000 Hz; below is infrasound, above is ultrasound. Reflected sound gives echoes, used and controlled in buildings.
2. Electromagnetic phenomena; electromagnetic oscillations and waves
Magnetic field of a current · Magnetic properties of matter and magnets · Electromagnetic induction · Electromagnetic waves
- Magnetic Effect of Electric Current – A wire carrying electric current makes a magnetic field around itself. The field forms circles around a straight wire, becomes nearly straight at the centre of a loop, and is uniform inside a solenoid, which then acts like a bar magnet.
- Magnetism: Magnets and the Compass – A magnet pulls iron, nickel and cobalt. Its pull is strongest at its two ends, the north (N) and south (S) poles. Like poles repel and unlike poles attract. Around a magnet is a magnetic field, drawn as lines from N to S; a compass needle lines up with it. Inside a magnet, tiny atomic magnets all point the same way. The Earth is a giant magnet, so a compass points north. An electric current in a coil makes an electromagnet.
- Force on a Current-Carrying Conductor, Motor and Induction – A wire carrying current inside a magnetic field feels a push. The push is biggest when the wire is at 90° to the field and zero when it is parallel. Fleming's left-hand rule gives its direction. A motor uses this push to spin a coil; a generator does the reverse and makes current by moving a coil or magnet.
- Electromagnetic Waves – A changing electric field acts like a current, called the displacement current, and it makes a magnetic field. A changing magnetic field makes an electric field. Together they travel as an electromagnetic (EM) wave at c = 3 × 10⁸ m/s, even through empty space. E and B are at right angles to each other and to the direction of travel, so EM waves are transverse. Sorted by wavelength, they form the spectrum: radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays.
3. Light phenomena
Rectilinear propagation of light · Reflection of light · Refraction of light · Lenses and optical instruments · Photometry, dispersion and colour · Wave properties of light
- How Light Travels – Light comes from sources like the Sun or a lamp and travels in straight lines. We see an object when light from it enters our eyes. Transparent things let light through, translucent things let some through, and opaque things block it. Blocked light makes shadows; a wide source gives a dark umbra and a lighter penumbra. A pinhole camera makes an upside-down image. Light is very fast: about 300 000 km every second.
- Reflection of Light: Plane and Spherical Mirrors – Light bounces off a shiny surface so that the angle of incidence equals the angle of reflection. A plane mirror gives a virtual, upright, same-size image as far behind as the object is in front. A concave mirror can give real or virtual images depending on where the object is; a convex mirror always gives a virtual, upright, smaller image. The mirror formula 1/v + 1/u = 1/f and magnification m = −v/u (with the New Cartesian sign convention) let you find the image without drawing.
- Refraction of Light: Laws, Refractive Index and the Glass Slab – Light changes speed when it goes from one transparent medium to another, and so it bends at the boundary (unless it hits along the normal). Going into an optically denser medium it slows down and bends toward the normal; coming out it speeds up and bends away. For a pair of media, sin i / sin r stays constant (Snell's law); this constant is the refractive index, which also equals the ratio of the speeds of light, n = c/v. In a rectangular glass slab the emergent ray is parallel to the incident ray but shifted sideways (lateral displacement).
- Spherical Lenses: Images, Lens Formula and Power – A convex lens is thick in the middle and bends parallel light to meet at its focus; a concave lens is thin in the middle and spreads light out as if from its focus. With two simple rays (one parallel to the axis, one through the optical centre) you can find the image for any object position. A convex lens gives real, inverted images when the object is beyond F₁ and a virtual, erect, enlarged image inside F₁; a concave lens always gives a virtual, erect, diminished image. The lens formula 1/v − 1/u = 1/f, magnification m = v/u and power P = 1/f (in metres, unit dioptre) let you solve lens numericals.
- Refraction Through a Prism, Dispersion of Light and the Rainbow – A glass prism bends light twice, both times towards its base; the total turn is the angle of deviation. Each colour in white light bends by a slightly different amount (violet most, red least), so a prism fans white light out into a spectrum, VIBGYOR. An upside-down second prism joins the colours back into white. Raindrops act like tiny prisms plus a mirror, which gives us the rainbow.
4. Atomic and nuclear phenomena
Model of the atom · Atomic nucleus and isotopes · Radioactivity and radiation safety · Nuclear reactions and energy
- Structure of the Atom – An atom has a tiny, heavy, positive nucleus made of protons and neutrons. Electrons move around it in fixed shells K, L, M, N. The number of protons (Z) tells the element; protons + neutrons give the mass number (A). Outer electrons decide valency. Isotopes share Z; isobars share A.
- Nuclear Physics: the Nucleus and Radioactivity – The nucleus holds protons (Z) and neutrons (N); mass number A = Z + N. Isotopes have the same Z but different N. Unstable nuclei decay at random: alpha decay removes 2 protons and 2 neutrons (A − 4, Z − 2), beta-minus decay turns a neutron into a proton and an electron (Z + 1), and gamma is energy only. Half-life is the time for half the nuclei in a sample to decay.
- Radioactivity: Alpha, Beta, Gamma and Half-Life – Some atomic nuclei are unstable. They give out radiation at random to become more stable. This is radioactive decay. Alpha (2 protons + 2 neutrons), beta (a fast electron) and gamma (a wave of energy) are the three main kinds. Half-life is the time for half of the unstable nuclei to decay.
5. Physics and astronomy in human life
Physics as the basis of the scientific world view · Structure and evolution of the Universe · Physics, safety and technology
- Nature of Science: How Scientific Knowledge Is Built and Changed – Science is a way of knowing that rests on evidence anyone can check. Scientists observe, infer, test ideas that could be proved wrong, and let other experts check their work. Laws describe what happens; theories explain why. Scientific knowledge is reliable but always open to change, and sometimes a whole way of seeing (a paradigm) is replaced.
- Science, Technology and Society: How Discoveries Change Our Lives – Science finds out how nature works; technology uses that knowledge to make tools and solve problems. Society shapes science too, by asking questions, paying for research and making rules. Big changes such as the printing press, the steam engine, electricity, vaccines and the internet changed how people work, live and think. Every technology has benefits and risks. To decide wisely we look at evidence, weigh benefits against risks, ask who gains and who loses, think about ethics and the future, and use safety rules.