Units & Significant Figures

Physics 1: Section I.4 to I.7

What are the seven fundamental physical quantities and SI base units?

Mass = kilogram (kg)

Time = second (s)

Length = meter (m)

Thermodynamic temperature = kelvin (K)

Amount of a substance = mole (mol)

Electric current = ampere (A)

Luminous intensity = candela (cd)

What is the SI base unit for mass?

Kilogram

What is the SI base unit for time?

Second (s)

What is the SI base unit for length?

Meter (m)

What is the SI base unit for thermodynamic temperature?

Kelvin (K)

What is the SI base unit for an amount of substance?

Mole (mol)

What is the SI base unit for electric current?

Ampere (A)

What is the SI base unit for luminous intensity?

Candela (cd)

Electric charge:

Coulomb (C = A x s)

Force:

Newton (N = kg x m² x s-² )

Energy, Work, Heat:

Joule (J = N x m = kg x m² x s-²

Area:

Meter squared (m²)

Volume:

Meter cubed (m³)

Density:

Kilogram per meter cubed (kg/m³)

Speed, Velocity:

Meter per second (m/s)

Momentum:

Kilogram meter per second (kg x m/s)

What is a second (s)?

The duration of the period of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

What is a meter (m)?

The distance traveled by light in a vacuum in 1/299,792,458 seconds

What is a kilogram?

The mass defined by setting the Planck constant h exactly to 6.62607015 × 10^-34 J x s (kg x m² x s^-1), given the definitions of the meter and second

From Artifacts to Constants: Second

Earths rotation —> year length —> cesium atom vibrations

From Artifacts to Constants: Meter

Earths meridian —> platinum bar —> speed of light

From Artifacts to Constants: Kilogram

Platinum cylinder —> Planck’s constant

What is the symbol and power of 10 of mega?

M, 10^6

What is the symbol and power of 10 of kilo?

k, 10³

What is the symbol and power of 10 for centi?

c, 10^-2

What is the symbol and power of 10 milli?

m, 10^-3

What is the symbol and power of 10 micro?

μ, 10^-6

1 mi=

5280 ft

1 ft=

12 in.

1 in.=

2.54 cm

1 y=

265.24 d

1 d=

24 h

1 h=

60 min

1 min=

60 s

1 lb=

4.448s N

What is scientific notation?

The vast range of quantities that occur in physics is best expressed using
scientific notation: an ordinary-sized number (between one and ten)
multiplied by a power of 10

What is a significant figure?

A recorded or measured digit

What are the multiplication and division rules for significant figures?

Perform the operation with no regard to sig figs. Round to the smaller number of sig figs.

What are the addition and subtraction rules for significant figures?

Perform the operation with no regard to significant figures. Round to the rightmost place that is determined from significant figures in both operands

How do you avoid round-off errors?

Always keep 2 extra digits for intermediate results. Subscripting guard digits can be helpful

What are units matter?

SI base units and prefixes that help us scale measurements