Physical Quantities and Measurements

A quantity with a numerical magnitude and a unit:

Physical quantity

Why is 36.5 degrees celsius a physical quantity?

It has a numerical magnitude (36.5) and a unit (degrees celsius)

Why is 180 cm a physical quantity?

It has a numerical magnitude (180) and a unit (cm)

Two types of physical quantities:

Base and derived

Fundamental quantities are the ______ of derived quantities

Building blocks

How are fundamental quantities measured?

Directly

The quantities on the basis of which other quantities are expressed:

Fundamental quantities

The quantities that are expressed in terms of base quantities:

Derived quantities

Example of fundamental and derived quantities of a book:

Length and width are fundamental quantities, area is derived quantities

7 fundamental quantities in physics:

Mass, length, time, current, temperature, luminous intensity, amount of substance

Fundamental quantities are also called:

Base quantities

Unit of mass:

Kilogram

Symbol for mass:

kg

Unit for length:

Meter

Symbol for meter:

m

Unit for time:

Second

Symbol for second:

s

Unit for current:

Ampere

Symbol for ampere:

A

Unit for temperature:

Kelvin or celsius

Symbol for kelvin:

K

Symbol for celsius:

C

Unit for luminous intensity:

Candela

Luminous intensity means:

Brightness of something

Symbol for candela:

Cd

Derived quantities are the result of:

Combining fundamental quantities

How to combine fundamental quantities to get derived quantities?

By multiplying or dividing them

Unit for amount of substance:

Mole

Symbol for amount of substance:

mol

How do derived quantities link to other quantities?

Through an equation

What does the equation of derived quantities enable us to do?

Express a derived unit in terms of base-unit equivalent

Examples of using equations of derived quantities to express a derived unit in terms of base-unit equivalent:

F=ma so Newton = kg m s^-2

P=F/A so Pascal = kg m s^-2 / m² = kg m^-1 s^-2

SI unit stands for:

International system of units

Derived quantities include:

Area, volume, speed/velocity, acceleration, density, amount concentration, force, work/energy, power, pressure, frequency, momentum, electrical charge, potential difference, resistance

Base equivalent units of area:

Square meter (m²)

Base equivalent units of volume:

Cubic meter (m³)

Base equivalent units of speed/velocity:

Meter per second (m/s or ms^-1)

Base equivalent units of acceleration:

Meter per second squared (m/s/s or ms^-2)

Base equivalent units of density:

Kilogram per cubic meter (kg m^-3)

Base equivalent units of amount concentration:

Mole per cubic meter (mol m^-3)

Base equivalent units of force:

kg m s^-2 (Newton)

Base equivalent units of work/energy:

kg m² s^-2 (Joule)

Base equivalent units of power:

kg m² s^-3 (Watt)

Base equivalent units of pressure:

kg m^-1 s^-2 (Pascal)

Base equivalent units of frequency:

s^-1 (Hertz)

Density is defined as:

mass (kg) / volume (m³)

Momentum is defined as:

mass (kg) x velocity (m s^-1)

Force is defined as:

mass (kg) x acceleration (m s^-2)

Pressure is defined as:

Force (kg m s^-2 or N) / area (m²)

Work (energy) is defined as:

Force (kg m s^-2 or N) x distance (m)

Power is defined as:

Work (kg m^-2 s^-2 or J) / time (s)

Electrical charge is defined as:

Current (A) x time (s)

Potential difference is defined as:

Energy (kg m^-2 s^-2 or J) / charge (As or C)

Unit for momentum:

kg m s^-1

Unit for electrical charge:

As or coulomb (C)

Resistance is defined as:

Potential difference (kg m² A^-1 s^-3 or V) / Current (A)

Unit for potential difference:

kg m² A^-1 s^-3 (JC^-1) or Volt

Unit for resistance:

kg m² A^-2 S^-2 s^-3 (VA^-1) or ohm (Ω)

7 prefixes:

Giga, mega, kilo, centi, milli, micro, nano

Abbreviation for giga:

G

Abbreviation for mega:

M

Abbreviation for kilo:

k

Abbreviation for centi:

c

Abbreviation for milli:

m

Abbreviation for micro:

µ

Abbreviation for nano:

n

Power of ten for giga:

10^9

Power of ten for mega:

10^6

Power of ten for kilo:

10³

Power of ten for centi:

10^-2

Power of ten for milli:

10^-3

Power of ten for micro:

10^-6

Power of ten for nano:

10^-9

Area is derived from:

Length x width

Volume is derived from:

Length x width x height

Speed/velocity is derived from:

Distance / time

Acceleration is derived from:

Change in velocity over time

Frequency is derived from:

Cycles over time

Instrument to measure length:

Measure stick / ruler

Instrument to measure time:

Stopwatch

Instrument to measure force:

Force spring

A straight line on a scatter plot that best represents the relationship between two sets of data points

Line of best fit

Two types of errors in experiments:

Systematic and random

Systematic error is a result of:

Device error

Random error is a result of:

Reaction time errors