Newton's Laws of Motion

  • Newton's first law of motion, also called the law on inertia, states that an object continues in its state of rest or of uniform motion unless compelled to change that state by an external force.
  • Newton's second law of motion states that if a net force acts on an object, it will cause an acceleration of that object.
  • Newton's third law of motion states that for every action there is an equal and opposite reaction.

Kepler's Laws of Planetary Motion

  • The law of orbits: All planets move in elliptical orbits with the sun at one focus.
  • The law of areas: A line joining a planet and the sun sweeps out equal areas in equal time.
  • The law of periods: The square of the period (T) of any planet is proportional to the cube of the semi-major axis (r) of its orbit, or T 2=(4π2/GM) r3, where M is the mass of the planet.

Einstein Postulates of Special Relativity

  • The laws of physics are the same in all inertial reference frames.
  • The speed of light is the same regardless of the frame of reference of the observer.

Other Principles and Laws

Pascal's principle: The pressure applied at one point in an enclosed fluid under equilibrium conditions is transmitted equally to all parts of the fluid.

Archimedes' principle: The magnitude of a buoyant force on a completely or partially submerged object always equals the weight of the fluid displaced by the object.

International System of Units

Quantity SI Unit American Unit Conversion (if applicable)
Length Meter (m) Foot (ft) 1 m = 3.281 ft
Time Second (s) Second (s) n/a
Mass Kilogram (kg) Pound (lb) 1 kg =2.205 lb
Electric current Ampere (A) Ampere (A) n/a
Amount Mole (mole) Mole (mole) n/a
Temperature Celsius (°C)
or Kelvin (K)
Fahrenheit (°F) °C = 59F - 32°)


Common Formulas

Name Abbrev. Formula
Speed of light c 3.0 ×108 m/s
Gravitational constant G 6.67 × 10-11 Nm2/kg2
Electron and proton charge e 1.6 × 10-19 C
Boltzmann's constant k 1.38 × 10-23 J/K
Gas constant R 8.31 J / mole K
Permittivity of free space o 8.85 × 10-12 C2 / Nm
Permeability constant µo 1.26 × 10-6 T m / A
Avagadro's number N 6.02 × 1023
Electron mass me 9.11 × 10-31 kg
Planck's constant h 6.63 × 10-34 J s



Prefix Abbrev. Value
nano- n 10-9
micro- µ 10-6
milli- m 10-3
centi- c 10-2
kilo- k 103
mega- M 106

Pop Quiz!

If a varies directly as b and a is 6 when b is 9, find b when a is 8.

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