Angola Military Technical Institute (ISTM) Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Quadratic formula

For ax²+bx+c=0 with a≠0, the roots are x = [−b ± √(b²−4ac)]/(2a); the discriminant b²−4ac determines how many real roots exist.

Pythagorean theorem

In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides: a²+b²=c², where c is opposite the right angle.

Arithmetic progression sum

The sum of the first n terms of an arithmetic progression is Sₙ = n(a₁+aₙ)/2, where a₁ is the first term and aₙ the nth term.

Derivative of xⁿ

The derivative of xⁿ with respect to x is n·x^(n−1) for any real exponent n, a core rule of differential calculus.

Newton's second law

The net force on a body equals its mass times its acceleration, F = m·a; force and acceleration point in the same direction.

Ohm's law

For a conductor at constant temperature, the voltage across it equals the current through it multiplied by its resistance: V = I·R.

Kinetic energy

The energy a body possesses due to its motion, given by KE = ½mv², where m is mass in kilograms and v is speed in m/s.

Wave equation

The speed of a wave equals its frequency multiplied by its wavelength: v = f·λ, with f in hertz and λ in metres.

Universal gravitation

Every mass attracts every other mass with force F = G·m₁m₂/r², where G ≈ 6.67×10⁻¹¹ N·m²/kg² and r is the separation.

Avogadro's number

One mole of any substance contains 6.022×10²³ elementary particles; this constant links molar mass to the number of atoms or molecules.

Molarity

Molarity is the concentration of a solution expressed as moles of solute per litre of solution, abbreviated M and measured in mol/L.

pH scale

pH = −log[H⁺]; values below 7 are acidic, 7 is neutral, and above 7 is basic when measured at 25 degrees Celsius.

Oxidation and reduction

Oxidation is the loss of electrons (oxidation number increases); reduction is the gain of electrons (oxidation number decreases) in a redox reaction.

Ideal gas law

For an ideal gas, pressure times volume equals moles times the gas constant times absolute temperature: PV = nRT.

Ionic versus covalent bonds

Ionic bonds form by electron transfer between a metal and a nonmetal; covalent bonds form by electron sharing, usually between nonmetals.

Crase rule

In Portuguese, the grave accent marks the contraction of preposition 'a' with article 'a(s)'; it does not occur before verbs, masculine nouns, or personal pronouns.

Sujeito e predicado

O sujeito é o termo sobre o qual se declara algo na oração; o predicado é o termo que contém o verbo e a informação dada sobre o sujeito.

Verbal concordance

In Portuguese, the verb agrees with the subject in person and number; a compound subject normally takes a plural verb.

Portuguese word classes

The ten classes are substantivo, artigo, adjetivo, numeral, pronome, verbo, advérbio, preposição, conjunção, and interjeição.

Oxytone accent rule

Portuguese words stressed on the last syllable take an accent when ending in a(s), e(s), o(s), em, or ens; all proparoxytones are accented.

Present perfect

Formed with have/has plus the past participle, it describes a past action connected to the present, often with 'since' or 'for'.

First conditional

Structure if + present simple followed by will + bare infinitive, used for real or likely future conditions and their results.

Passive voice

Formed with a tense of 'be' plus the past participle; the object of the active sentence becomes the subject, as in 'The book was written'.

Comparative adjectives

Short adjectives form the comparative with -er (bigger); longer adjectives use 'more' (more interesting); 'than' introduces the comparison.

Angola independence date

Angola became independent on 11 November 1975, when the MPLA proclaimed the People's Republic of Angola and Agostinho Neto became president.

Angola borders

Angola is bordered by Namibia to the south, Zambia to the east, and the Democratic Republic of the Congo and Republic of the Congo to the north.

Cabinda

Cabinda is an Angolan enclave north of the Congo River mouth, separated from the rest of Angola by DRC territory and important for offshore oil.

Angolan civil war end

The Angolan civil war (1975–2002) ended after Jonas Savimbi's death and the Luena Memorandum, paving the way for peace and reconstruction.

Kwanza River

The Kwanza is Angola's longest river entirely within the country; it rises on the central plateau and flows into the Atlantic south of Luanda.

Contrapositive

The statement 'If not Q then not P' is logically equivalent to 'If P then Q', whereas the converse 'If Q then P' is not equivalent.

De Morgan's laws

The negation of 'P and Q' is 'not P or not Q'; the negation of 'P or Q' is 'not P and not Q'.

Percentage change

Percentage change equals (new value − old value) divided by old value, multiplied by 100; successive changes compound rather than simply add.