is an attribute of the dynamics
from which the
of the system can be derived.
Action Physics is the Study of Motion. Stillness is an
. Everything is moving.
If standing still on Earth you're moving 800 miles per second or
the processes causing willful
of a more or less complex kind.
all forces occur in pairs such that if one object exerts a force on
another object, then the second object exerts an equal and opposite
on the first. The third law is also more generally stated
as: "To every action there is always
opposed an equal reaction
: or the
mutual actions of two bodies upon each other are always equal, and
directed to contrary parts." The attribution of which of the two
the action and which is the reaction is arbitrary. Either of the two can
be considered the action, while the other is its associated reaction.
of Least Action
is a variational principle that, when
applied to the action of a mechanical system
, can be used to obtain the
for that system.
The units of
is the magnitude of its
(the rate of change
of its position). Acceleration
of an object is the rate of change of its position
with respect to a frame of reference, and is a function of time.
is the amount of elapsed time between two events.
D = V x T
Action has the
of Energy x Time, where a
follows simultaneously all possible paths
with amplitudes determined by the action. For the action
integral to be well defined the
has to be bounded in time and space.
is any interaction
that, when unopposed, will change the motion of an object. In other words,
a force can cause an object with mass to change its
includes to begin moving from a state of rest), i.e., to accelerate. Force
can also be described by intuitive concepts such as a push or a pull. A
force has both magnitude and direction, making it a vector quantity. It is
measured in the SI
and represented by the symbol F.
is a force that gives rise to an equilibrium in a
physical system. If the system is perturbed away from the equilibrium, the
restoring force will tend to bring the system back toward equilibrium. The
restoring force is a function only of position of the mass or particle. It
is always directed back toward the equilibrium position of the system. The
restoring force is often to in simple harmonic motion. The force which is
responsible to restore original size and shape is called restoring force.
is a force with the property that the work done in
moving a particle between two points is independent of the taken path.
Equivalently, if a particle travels in a closed loop, the net work done
(the sum of the force acting along the path multiplied by the
displacement) by a conservative force is zero. A conservative force is
dependent only on the position of the object. If a force is conservative,
it is possible to assign a numerical value for the potential at any point.
When an object moves from one location to another, the force changes the
potential energy of the object by an amount that does not depend on the
path taken. If the force is not conservative, then defining a scalar
potential is not possible, because taking different paths would lead to
conflicting potential differences between the start and end points.
example of a conservative force, while Frictional
is an example of a non-conservative force. Other examples of
conservative forces are: force in elastic spring, electrostatic force
between two electric charges, magnetic force between two magnetic poles.
The last two forces are called central forces as they act along the line
joining the centres of two charged/magnetized bodies. Thus, all central
forces are conservative forces.
is a system that, when displaced from
its equilibrium position, experiences a restoring force, F, proportional
to the displacement, x:
is used to refer to an inertial force (also called a
'fictitious' force) directed away from the axis of rotation that appears
to act on all objects when viewed in a
is a force that makes a body follow a curved path. Its direction
is always orthogonal to the motion of the body and towards the fixed point
of the instantaneous center of curvature of the path.
is an apparent force that acts on all masses whose
motion is described using a non-inertial frame of reference, such as a
rotating reference frame.
is the voltage developed by any source of electrical energy such
as a battery
. It is generally
defined as the electrical potential for a source in a circuit. A
device that supplies electrical energy is called electromotive force or
emf. Emfs convert chemical, mechanical, and other forms of energy into
electrical energy. The product of such a device is also known as emf.
is an inertial force (also called a
) that acts on objects that are in motion relative to
rotating reference frame
. In a reference frame with clockwise
rotation, the force acts to the left of the motion
of the object. In one
with anticlockwise rotation, the force acts to the right. Though
recognized previously by others, the mathematical expression for the
Coriolis force appeared in an 1835 paper by French scientist
Gaspard-Gustave de Coriolis
, in connection with the theory of
water wheels. Early in the 20th century, the term Coriolis force began to
be used in connection with meteorology
. Deflection of an object due to the Coriolis force is called the 'Coriolis effect'.
(youtube) By calibrating your
the world's biggest weight - 1,000,000 pounds of force. This machine
ensures planes don't break apart, jets provide required thrust, and
rockets make it to their destination.
is the force
applied perpendicular to the surface of an object per unit
area over which that force is distributed.
is the product of the mass and velocity of an
Moment of Inertia
determines the torque needed for a desired
angular acceleration about a rotational axis.
is the rotational analog of linear
momentum, which is a vector quantity defined as the product of an object's
mass, m, and its velocity, v. Linear momentum is denoted by the letter p
and is called “momentum” for short.What IS Angular Momentum
is the resistance of any physical object to any change in its state of
motion (this includes changes to its speed, direction or state of rest).
Inertia is also defined as the tendency of objects to keep moving in a
straight line at a constant velocity
of matter by which it continues in its existing state of rest or uniform
in a straight line, unless that state is
changed by an external force
Moments of Inertia
is the mass moment of inertia, usually denoted by
I, measures the extent to which an object resists rotational acceleration
about a particular axis, and is the rotational analogue to mass. Mass
moments of inertia have units of dimension ML2([mass] × [length]2). It
should not be confused with the second moment of area, which is used in
bending calculations. The mass moment of inertia is often also known as
the rotational inertia, and sometimes as the angular mass.
govern the principle of replacing physical quantities with
operators. Such replacements include energy and momentum, which can be
derived informally from taking the time and space derivities of the plane
wave function. These show a similarity to the
Heisenberg Uncertainty Principle
, which is any of a variety of
mathematical inequalities asserting a fundamental limit to the precision
with which certain pairs of physical properties of a
, known as
complementary variables, such as position x and momentum p, can be known.
is a pivoted
support that allows the rotation of an object about a single axis. A set
of three gimbals, one mounted on the other with orthogonal
be used to allow an object mounted on the innermost gimbal to remain
independent of the rotation of its support (e.g. vertical in the first
animation). For example, on a ship: the gyroscopes, shipboard compasses,
stoves, and even drink holders typically use gimbals to keep them upright
with respect to the horizon despite the ship's pitching and rolling.
The Space Travel
in the 1997 Movie named
, was a film adaptation of
is a spinning wheel or disc in which the axis of rotation is
free to assume any orientation by itself. When rotating, the orientation
of this axis is unaffected by tilting or rotation of the mounting,
according to the conservation of angular momentum. Because of this,
gyroscopes are useful for measuring or maintaining orientation.
is the angular displacement of the steering
axis from the vertical axis of a steered wheel in a car, motorcycle,
bicycle or other vehicle, measured in the longitudinal direction.
is a change in the orientation of the rotational
axis of a rotating body
is the commonly
in which a spinning ball (or cylinder) curves away from its principal
is an intrinsic form of angular momentum
elementary particles, composite particles (hadrons), and atomic nuclei.
is to revolve quickly and
repeatedly around one's own axis. Head Spin
The Proton Spins is the reason why Everything Spins. (above
is a circular movement of an object around a center
(or point) of rotation . A three-dimensional object always rotates around
an imaginary line called a rotation axis. If the axis passes through the
body's center of mass, the body is said to rotate upon itself, or spin.
Rotation around a Fixed Axis
is when a system expels or accelerates mass in one direction, the accelerated
mass will cause a force of equal magnitude but opposite direction on that
is a physical constant that is the
of action, central in quantum mechanics.
of an aircraft refers to the capabilities of a
design in terms of airspeed and load factor or altitude.
refers to the phenomenon of an arrow
traveling in the direction it is pointed at full draw, when it seems that
the arrow would have to pass through the starting position it was in
before being drawn, where it was pointed to the side of the target.
is the path that a moving object follows through space as a
function of time. The object might be a projectile or a satellite.
Trajectory of a Projectile
is the path that a thrown or
launched projectile or missile without propulsion will take under the
action of gravity, neglecting all other forces, such as friction from
is the tendency of a force to rotate an object
about an axis.
is the twisting of an object due to an applied
is expressed in newton per squared meter (Pa) or
pound per squared inch (psi) while torque is expressed in newton metres (N·m)
or foot-pound force (ft·lbf). In sections perpendicular to the torque
axis, the resultant shear stress in this section is perpendicular to the
twisting force -
is a manner of characterizing a twist or screw
of a moving frame around a curve. The torsion of a curve, as it appears in
the Frenet–Serret formulas, for instance, quantifies the twist of a curve
about its tangent vector as the curve evolves (or rather the rotation of
the Frenet–Serret frame about the tangent vector). In the geometry of
surfaces, the geodesic torsion describes how a surface twists about a
curve on the surface. The companion notion of curvature measures how
moving frames "roll" along a curve "without twisting.
is a pseudovector field that describes the local
spinning motion of a continuum
near some point (the tendency of something to rotate ), as would be seen
by an observer located at that point and traveling along with the flow.
local inertial frames are determined by the
large scale distribution of matter, as exemplified by this anecdote: You
are standing in a field looking at the stars. Your arms are resting freely
at your side, and you see that the distant stars are not moving. Now start
spinning. The stars are whirling around you and your arms are pulled away
from your body. Why should your arms be pulled away when the stars are
whirling? Why should they be dangling freely when the stars don't move?
Mach's principle says that this is not a coincidence—that there is a
physical law that relates the motion of the distant stars to the local
inertial frame. If you see all the stars whirling around you, Mach
suggests that there is some physical law which would make it so you would
feel a centrifugal force. There are a number of rival formulations of the
principle. It is often stated in vague ways, like "mass out there
influences inertia here". A very general statement of Mach's principle is
"Local physical laws are determined by the large-scale structure of the
was an Austrian physicist and philosopher, noted
for his contributions to physics such as study of shock waves. (18
February 1838 – 19 February 1916).
is when its speed is very close to
the speed of light c.
is the rate of change of velocity of an object with
respect to time. An object's acceleration is the net result of any and all
forces acting on the object, as described by Newton's Second Law. The SI
unit for acceleration is metre per second squared (m s−2). Accelerations
are vector quantities (they have magnitude and direction) and add
according to the parallelogram law. As a vector, the calculated net force
is equal to the product of the object's mass (a scalar quantity) and its
is a device that measures proper acceleration. Proper
acceleration, being the acceleration (or rate of change of velocity) of a
body in its own instantaneous rest frame, is not the same as coordinate
acceleration, being the acceleration in a fixed coordinate system. For
example, an accelerometer at rest on the surface of the Earth will measure
an acceleration due to Earth's gravity, straight upwards (by definition)
of g ≈ 9.81 m/s2. By contrast, accelerometers in free fall (falling toward
the center of the Earth at a rate of about 9.81 m/s2) will measure zero.
of an object is the rate of change of its position with respect to a frame
of reference, and is a function of time. Velocity is equivalent to a
specification of its speed and direction of motion (e.g. 60 km/h to the
an object is the magnitude of its velocity (the rate of change of its
position); it is thus a scalar quantity. The average speed of an object in
an interval of time
travelled by the object divided by
the duration of the interval; the instantaneous speed is the limit of the
average speed as the duration of the time interval approaches zero. Speed
has the dimensions of distance divided by time. The SI unit of speed is
the metre per second, but the most common unit of speed in everyday usage
is the kilometre per hour or, in the US and the UK, miles per hour. For
air and marine travel the knot is commonly used. The fastest possible
speed at which energy or information can travel, according to special
relativity, is the speed of light
in a vacuum
c = 299,792,458 metres per second (approximately
1,079,000,000 km/h or 671,000,000 mph). Matter cannot quite reach the
speed of light, as this would require an infinite amount of energy. In
, the concept of
rapidity replaces the classical idea of speed.
is the highest velocity attainable by an object as
it falls through a fluid (air is the most common example, but the concept
applies equally to any fluid).
of an object is the rate of change of its angular displacement with
respect to time. The SI unit of angular velocity is radians per second.
Angular velocity is usually represented by the symbol omega (ω, rarely Ω).
When the angular velocity is represented as a vector, its direction is
perpendicular to the plane of rotation, with its orientation
conventionally specified by the right-hand rule.
describes the motion of points (alternatively "particles"),
bodies (objects), and systems of bodies without consideration of the
masses of those objects nor the forces that may have caused the motion.
is the acceleration that charged
particles undergo when being repeatedly reflected, usually by a magnetic
mirror (see also Centrifugal mechanism of acceleration). This is thought
to be the primary mechanism by which particles gain non thermal energies
in astrophysical shock waves. It plays a very important role in many
astrophysical models, mainly of shocks including solar flares and
of action in the photon is not separated into a
separate piece of time and a separate piece of energy.
in the universe consists of a little piece (quantum)
of non-observable action. Light
Physics Math Information
is a weight suspended from a pivot so that it can swing freely. When a
pendulum is displaced sideways from its resting, equilibrium position, it
is subject to a restoring force due to gravity that will accelerate it
back toward the equilibrium position. When released, the restoring force
combined with the pendulum's mass causes it to oscillate about the
equilibrium position, swinging back and forth. The time for one complete
cycle, a left swing and a right swing, is called the period. The period
depends on the length of the pendulum and also to a slight degree on the
amplitude, the width of the pendulum's swing.
How To Make A
Pendulum Wave (Science Experiment / Physics Toy)
is a substance that exerts some force
or effect. An active and efficient cause; capable of producing a certain
is a change in position of an object with respect to time.
Motion is typically described in terms of
Motion of a body is observed by attaching a frame of reference to an
observer and measuring the change in position of the body relative to that
Newton's 3 Laws of Motion
If a body is at rest it remains at rest or, if it is in motion, it moves
with uniform velocity, until it is acted on by a resultant force.
The resultant force is equal to
mass times acceleration
. A resultant force, also called a net force, is a
force equal to the sum of all forces applied to an object
For every action, there is an
equal and opposite reaction
. Or every action always reacts in the opposite
Philosophiae Naturalis Principia Mathematica
is a work in
three books by Isaac Newton, in Latin, first published 5 July 1687. After
annotating and correcting his personal copy of the first edition, Newton
published two further editions, in 1713 and 1726. The Principia states
Newton's laws of motion, forming the foundation of classical mechanics;
Newton's law of universal gravitation; and a derivation of Kepler's laws
of planetary motion (which Kepler first obtained empirically). The
Principia is considered as one of the most important works in the history
Introduction to Motion
are equations that describe the behaviour of a
in terms of its
as a function of time. More specifically, the equations of
motion describe the behaviour of a physical system as a set of
mathematical functions in terms of dynamic variables: normally spatial
coordinates and time are used, but others are also possible, such as
momentum components and time. The most general choice are generalized
coordinates which can be any convenient variables characteristic of the
physical system. The functions are defined in a Euclidean space in
classical mechanics, but are replaced by curved spaces in relativity. If
the dynamics of a system is known, the equations are the solutions to the
differential equations describing the motion of the dynamics.
states that all forces occur in pairs such that if one object exerts a
force on another object, then the second object exerts an equal and
opposite reaction force on the first. The third law is also more generally
stated as: "To every action there is always opposed an equal reaction: or
the mutual actions of two bodies upon each other are always equal, and
directed to contrary parts." The attribution of which of the two forces is
the action and which is the reaction is arbitrary. Either of the two can
be considered the action, while the other is its associated reaction.
Body Motion (physics)
7 Myths About
is a vector that is the shortest
from the initial to the
final position of a point P. It quantifies both the distance and direction
of an imaginary motion along a straight line from the initial position to
the final position of the point. A displacement may be also described as a
'relative position': the final position of a point (Sf) relative to its
initial position (Si), and a displacement vector can be mathematically
defined as the difference between the final and initial position vectors.
is an area of science concerned with the behaviour of physical bodies when
subjected to forces or displacements, and the subsequent effects of the
bodies on their environment. Mechanics
is the branch of physics concerned with the motion of bodies in a frame of
reference. The technical aspects of doing something.
is a branch of applied mathematics (specifically
classical mechanics) concerned with the study of forces
and torques and their effect on motion, as opposed to kinematics, which
studies the motion of objects without reference to its causes. Isaac
Newton defined the fundamental physical laws which govern dynamics in
physics, especially his second law of motion.
is the branch of mechanics concerned with the forces that
cause motions of bodies.
refers to the dynamics of
vehicles, here assumed to be ground vehicles. Vehicle dynamics is a part
of engineering primarily based on
Spring back; spring
away from an impact.Rebound:
back from an impact.Bounce:
Move up and
Turn from a
straight course, fixed direction, or line of interest. Turn aside and away
from an initial or intended course.
is the power or the ability to move. Self-propelled
when acting there is a displacement of the point of application in the
direction of the force
. For example, when a ball is held above the ground
and then dropped, the work done on the ball as it falls is equal to the
weight of the ball (a force) multiplied by the distance to the ground (a
is the rate of doing work."
is the work done on a charged particle by an electric
field. The equation for 'electrical' work is equivalent to that of
Potentiality and Actuality
is a change or activity that represents the
of something happening. The inherent capacity for coming into
being. A possibility becomes real when knowledge of the requirements that
are needed to complete a task are available. Not to say something will
happen, it's saying that something could happen under the
conditions or requirements
is a short-lasting event in which the electrical
membrane potential of a
rapidly rises and falls, following a consistent trajectory.
is the difference in electric potential between the interior
and the exterior of a biological cell. With respect to the exterior of the
cell, typical values of membrane potential range from –40 mV to –80 mV.
is the amount of electric potential
that a unitary
point electric charge
would have if located at any point in space, and is
equal to the work done by an external agent in carrying a unit of positive
charge from the arbitrarily chosen reference point (usually infinity) to
that point without any acceleration.
is a potential energy (measured in joules) that
results from conservative Coulomb forces and is associated with the
configuration of a particular set of point charges within a defined
is energy possessed by a body by virtue of its position relative to
others, stresses within itself, electric charge, and other factors.
is the amplitude of potential, m is the
mass of the particle
, r is the
radial distance to the particle, and k is another scaling constant, so
that 1/km is the range. The potential is monotone increasing in r and it
is negative, implying the force is attractive. In the SI system, the unit
of the Yukawa potential is (1/m).
is the ability of a body to resist a distorting
influence or deforming force and to return to its original size and shape
when that influence or force is removed. Solid objects will deform when
adequate forces are applied on them. If the material is
, the object will return to its initial shape and size when
these forces are removed.
Somersaulting simulation for jumping bots
. New simulation methods
enable easier, faster design of elastic materials for robots and other
is possessing numerous
. The capacity for
coming into being
prospect and the possibility of future
aptitude that may be developed. Having the skills and
to do things well.
is the realizing of one's deepest desires and
. A satisfying and
worthwhile life well lived.
is an educational and psychological term
referring to the ability and preference of a person, particularly one of
excel in two or more different
. It can also refer to an individual whose interests span
multiple fields or areas, rather than being strong in just one. Such
traits are called multipotentialities, while "multipotentialites" has been
suggested as a name for those with this trait. By contrast, those whose
mostly within a single field are called "specialists
is a force with the property that the work done in moving a
particle between two points is independent of the taken path.
Equivalently, if a particle travels in a closed loop, the net work done
(the sum of the force acting along the path multiplied by the distance
travelled) by a conservative force is zero.
is a law of physics that describes force interacting between static
electrically charged particles.
is the region surrounding a local minimum of potential
energy. Energy captured in a potential well is unable to convert to
another type of energy (kinetic
in the case of a gravitational potential well) because it is
captured in the local minimum of a potential well. Therefore, a body may
not proceed to the global minimum of potential energy, as it would
naturally tend to due to
is when people perceive their
environment and events within it in terms of their
ability to act
Physics of Tennis
T-Handle in Zero-G, HD, free floating rotation showing a
bi-stable state due to intermediate moments of inertia
Science of Flight
is the process by which an object moves, through an
(the air in
the case of earth) or beyond it (as in the case of spaceflight) without
direct support from any surface. This can be achieved by generating
aerodynamic lift, propulsive thrust, aerostatically using buoyancy, or by
Time of Flight
is a property of an object, particle or acoustic,
electromagnetic or other wave. It is the time that such an object needs to
travel a distance through a medium. The measurement of this time (i.e. the
time of flight) can be used for a time standard (such as an atomic
fountain), as a way to measure velocity or path length through a given
medium, or as a way to learn about the particle or medium (such as
composition or flow rate). The traveling object may be detected directly
(e.g., ion detector in mass spectrometry) or indirectly (e.g., light
scattered from an object in laser doppler velocimetry).
is a powered, fixed-wing aircraft that is propelled forward by thrust from
a jet engine or propeller. Airplanes come in a variety of sizes, shapes,
and wing configurations.
is an aircraft (nearly always a fixed-wing aircraft)
propelled by jet engines (jet propulsion).
Dynamics of Flight
How Planes Work
The Science Behind Airplanes
Principles of Flight
Dynamics of Space Flight - NASA
HOW AIRPLANES FLY -
The Science Behind Flight
is a branch of
concerned with studying the motion of air, particularly
when it interacts with a solid object, such as an
Aerodynamics is a sub-field of fluid dynamics and
, and many aspects of aerodynamics theory are common to
these fields. The term aerodynamics is often used synonymously with gas
dynamics, with the difference being that "gas dynamics" applies to the
study of the motion of all gases, not limited to air.
states that an increase in the speed of a fluid
occurs simultaneously with a decrease in pressure or a decrease in the
fluid's potential energy. If the air flowing past the top surface of an
aircraft wing is moving faster than the air flowing past the bottom
surface, then Bernoulli's principle implies that the pressure on the
surfaces of the wing will be lower above than below. This pressure
difference results in an upwards lifting force.
Why Are Airplane
Wings Angled Backwards??
is exerted on a body by the air (or some other gas)
in which the body is immersed, and is due to the relative motion between
the body and the gas. Aerodynamic force arises from two causes: the normal
force due to the pressure on the surface of the body. The shear force due
to the viscosity of the gas, also known as skin friction. Pressure acts
locally, normal to the surface, and shear force acts locally, parallel to
the surface. The net aerodynamic force over the body is due to the
pressure and shear forces integrated over the total exposed area of the
body. When an airfoil (or a wing) is moving relative to the air it
generates an aerodynamic force, in a rearward direction at an angle with
the direction of relative motion. This aerodynamic force is commonly
resolved into two components.
or slipstreaming, is a technique where two
vehicles or other moving objects are caused to align in a close group
reducing the overall effect of drag due to exploiting the lead object's
slipstream. Especially when high speeds are involved, as in motor racing
and cycling, drafting can significantly reduce the paceline's average
energy expenditure required to maintain a certain speed and can also
slightly reduce the energy expenditure of the lead vehicle or object.
is a region in a fluid in which the flow is rotating around an
axis line, which may be straight or curved.
Density of Air
is the mass per unit volume of
. Air density, like air pressure, decreases with increasing
altitude. It also changes with variation in temperature or humidity.
based on the context in which it is used (aviation, geometry, geographical
survey, sport, and many more). As a general definition, altitude is a
, usually in the vertical or "up" direction, between a
reference datum and a point or object.
used when referring to points on the Earth's surface, while altitude or
geopotential height is used for points above the surface, such as an
aircraft in flight or a spacecraft in orbit
, and depth is used for points
below the surface.Wind
is the flow of gases on a large scale
is reported by the direction from which it originates. A northerly Wind
blows from the north to the south.
is a column of
rising air in the lower altitudes
, a form of
. Thermals are created by the uneven heating of Earth's surface
from solar radiation
, and are an
example of convection
, specifically atmospheric convection. The
, which in turn warms the air directly above it.
movement of groups of molecules within fluids such as gases and liquids,
including molten rock (rheid). Convection takes place through
, diffusion or both. Advection is the transport of a
substance by bulk motion. Hot Air
a type of friction, or fluid resistance, another type
of friction or fluid friction) is a force acting opposite to the relative
motion of any object moving with respect to a surrounding fluid.
is the fluid drag force that acts on
any moving solid body in the direction of the fluid freestream flow.
is a dimensionless quantity that is used to quantify the drag or
resistance of an object in a fluid environment, such as air or water. It
is used in the drag equation in which a lower drag coefficient indicates
the object will have less aerodynamic or hydrodynamic drag. The drag
coefficient is always associated with a particular surface area.
sometimes called air resistance, a type of friction, or fluid resistance,
another type of friction or fluid friction) is a force acting opposite to
the relative motion of any object moving with respect to a surrounding
fluid. This can exist between two fluid layers (or surfaces) or a fluid
and a solid surface. Unlike other resistive forces, such as dry friction,
which are nearly independent of velocity, drag forces depend on velocity.
Drag force is proportional to the velocity for a laminar flow and the
squared velocity for a turbulent flow. Even though the ultimate cause of a
drag is viscous friction, the turbulent drag is independent of viscosity.
is the force
resisting the relative
motion of solid surfaces,
layers, and material elements sliding against each other. There
are several types of friction: Dry friction
is a force that opposes the relative lateral motion of two solid surfaces
in contact. Dry friction is subdivided into static friction ("stiction")
between non-moving surfaces, and kinetic friction between moving surfaces.
With the exception of atomic or molecular friction, dry friction generally
arises from the interaction of surface features, known as asperities.
describes the friction
between layers of a viscous
that are moving relative to each other.
is a case of fluid
friction where a lubricant fluid separates two solid surfaces.
is a component of drag, the
force resisting the motion of a fluid across the surface of a body.
is the force resisting
motion between the elements making up a solid material while it undergoes
When surfaces in contact move relative to each other, the
friction between the two surfaces converts
(that is, it
converts work to heat
). This property can have dramatic consequences.
Laser-cooled ions contribute to better understanding of friction
is the process of a laminar flow becoming
, which is a flow regime in fluid dynamics characterized by
chaotic changes in pressure and flow velocity. It is in contrast to a
laminar flow regime, which occurs when a fluid flows in parallel layers,
with no disruption between those layers.
describes the flow of fluids (liquids and gases).
is the front window generally made of laminated safety glass, a type of
treated glass, which consists of two (typically) curved sheets of glass
with a plastic layer laminated between them for safety, and are bonded
into the window frame. Motorbike windshields are often made of high-impact
aeronautical term that stands for "Ceiling and
Why are plane
is a location in an object where stress is concentrated.
An object is strongest when force is evenly distributed over its area, so
a reduction in area, e.g., caused by a crack, results in a localized
increase in stress. A material can fail, via a propagating crack, when a
concentrated stress exceeds the material's theoretical cohesive strength.
The real fracture strength of a material is always lower than the
theoretical value because most materials contain small cracks or
contaminants (especially foreign particles) that concentrate stress.
Fatigue cracks always start at stress raisers, so removing such defects
increases the fatigue strength.
Center of Mass
of a distribution of
in space is the unique
point where the weighted relative position of the distributed mass sums to
zero, or the point where if a force is applied it moves in the direction
of the force without rotating. The distribution of mass is
of mass and the
average of the weighted position
coordinates of the distributed mass defines its coordinates. Calculations
in mechanics are often simplified when formulated with respect to the
center of mass. It is a hypothetical point where entire mass of an object
may be assumed to be concentrated to visualise its motion. In other words,
the center of mass is the particle equivalent of a given object for
application of Newton's laws of motion
is a process in which conditioned air is pumped into
the cabin of an aircraft or spacecraft, in order to create a safe and
comfortable environment for passengers and crew flying at high altitudes.
For aircraft, this air is usually bled off from the gas turbine engines at
the compressor stage, and for spacecraft, it is carried in high-pressure,
often cryogenic tanks. The air is cooled, humidified, and mixed with
recirculated air if necessary, before it is distributed to the cabin by
one or more environmental control systems. The cabin pressure is regulated
by the outflow valve.
Wiz KidsWeather effects
STRAPPED INTO A
FALLING HELICOPTER - Smarter Every Day 154
is a state of flight in which the main rotor system
of a helicopter or similar aircraft turns by the action of air moving up
through the rotor, as with an autogyro, rather than engine power driving
the rotor. (adjust collective pinwheel).
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