Chapter 1 Physics of the Earth
MOSTLY NOT IN TEXTBOOK
Physics - Basic Terms
Mass
Density
Weight
Metric system:
meter-kilogram-second centimeter-gram-second
Orders of magnitude:
meter – millimeter, centimeter, kilometer, etc.
Velocity R = D/T
Speed
Acceleration mph/sec m/sec2 = (m/sec)/sec
Force F=ma mass * acceleration
Inertia = mass * velocity
Newton’s second law of motion F=ma
Proportional versus inversely proportional
Newton – an unit of force
Measurement of mass
Gravity law - F = G (m1*m2 / s 2)
Acceleration due to gravity (g)
Beam balance
Spring balance
Newton’s second law of motion F=ma
Proportional versus inversely proportional
Newton – an unit of force
Measurement of mass
Gravity law - F = G (m1*m2 / s 2)
Acceleration due to gravity (g)
Beam balance
Spring balance
Mass (concept)
Mass = amount of matter an object contains
Mass of the Earth = 5.96
x 1024 kg
(on earth 1 lb = 0.454 kg, but remember, lb is a weight term)
Mass is Independent of:
· Temperature
· Pressure
· Location
Number and
mass of atoms in an object
different number of protons and
neutrons in the nucleus
(nucleus has 99.99% of
mass of the atom)
Mass and weight
Weight is relative to gravity
Would you have the same mass
on the moon?
On Jupiter?
In interstellar space?
Would your weight change?
Density (concept)
Density
= Mass / Volume
Units
are grams per
cubic centimeter (g / cm3)
Ice = 0.917 g/cm3
Water = 1.0 g/cm3-
Remember this one
Iron = 7.86 g/cm3
Gold = 19.3 g/cm3
The metric system links measurement of volume and mass: by definition, one cm3 of pure water (at a specific temperature and pressure) has a mass of 1.0 gram
Comparing the density of objects: float or sink in a fluid, depending upon the
relative density
** Buoyancy – upward force of a
lower-density object **
Density-driven circulation in fluids on Earth:
Atmosphere
Oceans
Mantle
D = M / V or rearrange to M = D * V
*** Check to see if units work ***
Force (concept)
A Push or Pull (with or without motion & contact)
Inertia or Momentum (concept)
The Resistance of an object to:
- change in direction or
- its state of rest
An object at rest will remain at rest…
An object in motion will remain in
motion at a constant velocity…
unless: …acted upon by some force
Speed and velocity
Speed is how
fast an object is moving
R = D/T rate = distance / time
miles per hour meters per second
Rearrange: D =
R*T T = D/R
*** remember the units ***
Velocity has
both speed and direction
Newton’s Second Law of Motion
Force = Mass * Acceleration [F = MA] or A = F / M
How are force and mass related to acceleration?
1. Acceleration is proportional to force
if mass is constant,
as force increases, acceleration increases
as force decreases, acceleration decreases
2. Acceleration is inversely
proportional to mass
if force is constant,
as mass increases, acceleration decreases
as mass decreases, acceleration increases
Velocity is a
vector, with components of speed and direction
V (velocity) =
change in D (distance) / change in T (time)
Units: meters/sec miles/hour
Acceleration
means changing velocity
Either positive (increasing) or
negative (decreasing)
A
(acceleration) = change in V (velocity) / change in T (time)
Units: meters / sec2
but think of this as meters / sec per second
Acceleration
by the force of gravity on Earth = 9.81 m/sec per second
idea of terminal velocity – when wind
resistance = downward force
Force = mass *
acceleration
units: kg * m/sec2 , which is one Newton
weight is really a force (not simply
mass)
Force – equal and
opposite
A force must be applied to move the
car forward,
but a force also must be exerted in the opposite direction
(wheels pushing against the
pavement)
Gravity
F = G
M1 * M2 /
S2
F = force of gravity