Download Definitions - Planetscience

Definitions !
Forces and Motion
Velocity !
Velocity is the rate of change of displacement,
with respect to time.
Acceleration !
Acceleration is the rate of change of velocity,
with respect to time.
Scalars !
Scalar quantities have only a magnitude.
Vectors !
Vectors, unlike scalars, have both a magnitude
and a direction.
Weight !
The weight of a body is the force of gravity
acting on a body, it is measured in Newton’s
(N).
Power !
Power is the work done per unit of time.
Power (W) = work done
time
Power (W) = Force x Speed
Pressure !
The force being applied per unit area.
Pressure (Pa) = Force
Area
Density !
Density can be defined simply as “mass per
unit volume”.
Density (Kg/m3) = Mass
Volume
Stress !
The force being applied per unit area.
Stress (Pa) = Force
Area
Strain !
The strain on an object is the extention
against the original length.
Young’s Modulus
Young’s Modulus, measured in “Pa” (Pascal)
is simply:
Young’s Modulus = Stress
Strain
Moments !
A Moment is the product of force and the
perpendicular distance from a pivot.
Watt !
One watt is one joule of energy transferred per
second.
Speed !
Speed is the rate of change of distance.
Speed = Distance
Time
The Four Equations of Motion !
v = u + at
v = u² + 2as
S = (u+v)t
2
S = ut + ½ at²
Potential Energy !
Potential energy = Mgh (J)
Kinetic Energy !
Kinetic Energy = ½Mv² (J)
Work Done !
Work Done = Force X Distance Moved (J)
Newton’s 3 Laws of Motion
Law Of Inertia
Every object in a state of uniform motion tends to remain in that
state of motion unless an external force is applied to it.
Force = Mass x Acceleration
The relationship between an object's mass (m), its acceleration
(a), and the applied force (f) is “F = ma”. Acceleration and
force are vectors. In this law the direction of the force vector
is the same as the direction of the acceleration vector.
For every action, there is an equal reaction
(e.g. Stepping off a boat onto the shore/dock causes the boat to
drift back in the opposite direction. Thus leaving the person
in the water, IF they are not careful!)