KUUMAT Nepal flashcards

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

Newton's second law

The net force on a body equals its mass times its acceleration, F = ma. Force and acceleration point in the same direction; zero net force means constant velocity.

Projectile maximum range

For a projectile launched over level ground at speed u, horizontal range R = u²sin2θ/g is greatest at 45°, where sin2θ equals one.

Ohm's law

Current through a conductor is proportional to potential difference across it at constant temperature, V = IR, with R in ohms when V is volts and I is amperes.

Photoelectric equation

Maximum kinetic energy of emitted electrons is K_max = hf − φ, where φ is the work function. Emission occurs only when frequency exceeds the threshold f₀ = φ/h.

Centripetal acceleration

A body moving in a circle of radius r at speed v accelerates toward the centre with magnitude v²/r, equal to ω²r when angular velocity ω is used.

Half-life

The time in which half the radioactive nuclei in a sample decay. After n half-lives the remaining fraction is (1/2)ⁿ, and t½ = 0.693/λ.

Mole concept

One mole contains 6.022×10²³ particles and has a mass in grams equal to the substance's molar mass. One mole of ideal gas occupies 22.4 L at STP.

Molarity

Molarity is moles of solute per litre of solution. Dilution keeps moles constant, so M₁V₁ = M₂V₂ when solvent is added.

pH scale

pH = −log[H⁺]. At 25 °C, pH + pOH = 14; values below 7 are acidic, above 7 basic, and each unit means a tenfold change in hydrogen ion concentration.

Le Chatelier's principle

When a system at equilibrium is disturbed, it shifts in the direction that opposes the change. Adding heat favours the endothermic direction; extra pressure favours fewer gas moles.

Hybridisation and shape

Steric number predicts hybridisation: 2 gives sp and linear, 3 gives sp² and trigonal planar, 4 gives sp³ and tetrahedral. Lone pairs reduce bond angles below ideal values.

Oxidation number

A bookkeeping charge per atom. Free elements are zero, oxygen is usually −2, hydrogen usually +1, and the sum equals the ion's overall charge.

Ideal gas law

PV = nRT relates pressure, volume, moles and absolute temperature. Use R = 0.0821 L·atm/(mol·K) or 8.314 J/(mol·K) and convert °C to kelvin.

Photosynthesis overall equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Light reactions in thylakoids split water and release oxygen; the Calvin cycle in the stroma fixes carbon.

Monohybrid F₂ ratio

Crossing two heterozygotes for one gene gives a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio in the offspring.

Xylem versus phloem

Xylem transports water and dissolved minerals upward from roots, driven largely by transpiration pull. Phloem translocates sugars from sources to sinks using energy.

Insulin and glucagon

Insulin from pancreatic beta cells lowers blood glucose by promoting uptake and glycogen storage. Glucagon from alpha cells raises glucose by releasing stored glycogen.

Binomial nomenclature

Each species has a two-part Latin name: capitalised genus followed by lowercase species epithet, both italicised, for example Homo sapiens.

Glycolysis

The first stage of respiration, occurring in the cytoplasm, splits one glucose into two pyruvate molecules and yields a net gain of two ATP and two NADH.

Action potential

A nerve impulse begins with sodium ions entering the axon, depolarising the membrane, followed by potassium efflux that repolarises it before the resting potential is restored.

Transpiration pull

Water evaporating from leaf stomata creates tension in the xylem, pulling a continuous water column upward through cohesion and adhesion between water molecules and vessel walls.

Quadratic formula

Roots of ax² + bx + c = 0 are x = [−b ± √(b² − 4ac)]/2a. The discriminant b² − 4ac determines whether roots are real, equal or complex.

Sum and product of roots

For ax² + bx + c = 0 with roots α and β, α + β = −b/a and αβ = c/a. These let you form a quadratic from its roots.

Arithmetic progression sum

For first term a, common difference d and n terms, the nth term is a + (n−1)d and the sum is n/2[2a + (n−1)d].

Combination formula

nCr = n!/[r!(n−r)!] counts selections where order does not matter. Use nPr = n!/(n−r)! instead when arrangement order matters.

Sine rule

In any triangle, each side divided by the sine of its opposite angle is constant: a/sinA = b/sinB = c/sinC, equal to twice the circumradius.

Sphere and cone volume

A sphere of radius r has volume 4/3πr³ and surface area 4πr². A cone with base radius r and height h has volume ⅓πr²h.

Divisibility by 11

A number is divisible by 11 when the difference between the sums of its alternating digits is zero or a multiple of 11.

Average speed equal distances

When two equal distances are covered at speeds v₁ and v₂, the average speed is the harmonic mean 2v₁v₂/(v₁+v₂), not the arithmetic mean.

Probability addition rule

For two events, P(A or B) = P(A) + P(B) − P(A and B). The subtraction removes outcomes counted in both events.

Successive percentage change

Two successive changes multiply as factors: a 20% rise then a 10% fall gives 1.2 × 0.9 = 1.08, a net 8% increase.