RRB JE CBT 1 science revision notes: formulas, SI units and worked checks

Convert km/h to m/s by multiplying by 5/18; reverse with 18/5. Average speed is total distance divided by total time. For equal distances travelled at speeds u and v, it is 2uv/(u+v), not generally their arithmetic mean.

Use F = ma, momentum p = mv, kinetic energy = ½mv² and power = work/time. For constant force parallel to motion, work = force × displacement. The SI units are newton for force, joule for energy/work and watt for power. Convert mass to kilograms before substituting. Speed is scalar; velocity includes direction. Zero instantaneous velocity does not necessarily mean zero acceleration.

Ohm’s law gives V = IR for an ohmic conductor under fixed physical conditions. Series resistances add; for two parallel resistors, equivalent R = R₁R₂/(R₁+R₂). Power P = VI, and with Ohm’s law P = I²R = V²/R.

A kilowatt-hour is energy: 1 kWh = 3.6 × 10⁶ J. It is not a power unit. For a rated appliance, the stated power corresponds to its rated operating conditions; do not reuse that power unchanged after a different voltage is applied without an appropriate model. Check whether a question asks for current, resistance, power or energy before choosing a formula.

For a temperature change without a phase transition, heat Q = mcΔT. During a phase change, use the latent-heat relation Q = mL where its assumptions apply. A one-degree Celsius temperature difference equals a one-kelvin difference, but absolute temperatures differ: kelvin = °C + 273.15.

Density = mass/volume; pressure = force/area. For 1 g/cm³, the SI density is 1000 kg/m³. Smaller area under the same force means greater pressure. In numerical questions, convert every input to a compatible unit before calculation rather than fixing units at the end.

For a neutral atom, protons equal electrons. Atomic number counts protons; mass number counts protons plus neutrons. Isotopes have the same atomic number and different mass numbers. Balance a chemical equation by changing coefficients, not by changing the substances’ chemical formulae.

At 25°C, neutral aqueous solutions have pH 7; acidic solutions are below 7 and basic solutions above 7. This familiar reference depends on temperature. In cells, mitochondria are associated with aerobic energy production, ribosomes with protein synthesis, and chloroplasts with photosynthesis in plants. Xylem transports water and minerals; phloem transports organic food substances. Test each pair in both directions instead of memorising only one prompt.

Read one section, close it and write the formulas with their units and one condition of use. Then attempt the original checks below. For each error, record whether the cause was recall, unit conversion, an unsuitable formula or arithmetic. Retry later with changed numbers.

The JE final-revision guide covers the wider study routine. The JE admit-card update links the official admission listing. ALP candidates should use their own city-slip update rather than the JE login.