1.2 system of unit

Front: What are the SI base units for mass, length, and time? (Include symbols)

Back: * Mass = kilogram (kg) (Note: it is NOT the gram!)

Length = metre (m)

Time = second (s)

Front: Name the SI base units used for measuring electric current and temperature.

Back: * Electric current = ampere (A)

Temperature = kelvin (K)

Front: What are the two effects of mass explained in the book?

Back: 1. Gravitational pull: All objects are attracted to Earth (greater mass = stronger pull).

2. Inertia: All objects resist changes to their motion (greater mass = greater resistance to speeding up, slowing down, or changing direction).

Front: Give the scientific notation (in kg) and an approximate real-world size for:

1 tonne (t)

1 gram (g)

1 milligram (mg)

Back: * 1 t = 10^3\text{ kg} (A medium-sized car)

1 g = 10^{-3}\text{ kg} (A banknote)

1 mg = 10^{-6}\text{ kg} (A human hair)

Front: Convert these units to metres using scientific notation:

1 km | 1 cm | 1 mm | 1 \mum | 1 nm

Back: * 1 km = 10^3\text{ m} (10 football pitches)

1 cm = 10^{-2}\text{ m}

1 mm = 10^{-3}\text{ m}

1 \mum (micrometre) = 10^{-6}\text{ m} (Bacteria)

1 nm (nanometre) = 10^{-9}\text{ m} (Atoms)

Front: Convert these short time units to seconds using scientific notation:

1 millisecond (ms)

1 microsecond (\mus)

1 nanosecond (ns)

Back: * 1 ms = 10^{-3}\text{ s}

1 \micro second = 10^{-6}\text{ s}

1 ns = 10^{-9}\text{ s}

Front: How are the standard second and standard metre accurately defined today?

Back: * Second: Defined by the frequency of an oscillation in the nucleus of a caesium atom.

Metre: Defined by the distance light travels in a vacuum in \frac{1}{299,792,458} of a second.

Front: What do these symbols stand for?

g, mg, t, \mum, ms

Back: * g = gram

mg = milligram

t = tonne

\mum = micrometre

ms = millisecond