Mechical Equilibrium
stable, without changes in motion, net force = 0, state of steadiness, no physical changes, not moving, forces add up to zero, moving at a constant speed
force
push or pull, needed to change an objects state of motion, example of vector quantity, a force is always a part of a mutual action that involves another force
net force
the combination of all forces acting on an object
tension
a stretched spring, "stretching force
weight
measured in newtons and pounds, the gravitational force acting on an object, depends on location, on the moon weight is 1/6th the less as it is on earth, if stone were in gravity free environment the stone would weigh zero, the force of gravity on an obje
vector
an arrow that represents the magnitude and direction of a quanitity
vector quantity
quantity that needs both magnitude and direction, force and acceleration are examples
scalar quantity
quantity described by magnitude only and has no direction, ex. time, area, and volume, speed
Equilibrium rule
whenever the net force on an object is zero, the object is said to be in mechanical equilibrium
support force
the upward force that balances the weight of an object on a surface, aka the normal force, for an object at rest on a horizontal surface, the support force must equal the objects weight
static equilibrium
objects at rest, mechanical equilibrium
dynamic equilibrium
objects moving at a constant speed in a straight-line path, mechanical equilibrium
resultant
the sum of two or more vectors, the resultant of two perpendicular vectors is the diagonal constructed with the two vectors as sides, pythagoream thym...knowing 3suared plus 4squared = csquared (the diagonal) use pythagoream thyrm to find that the resulta
parallelogram rule
to find the resultant of two non-parallel vectors, construct a parallelogram wherein the two vectors are adjacent sides. The diagonal of the parallelogram shows the resultant. to find vectors do the opposite with the resultant...make a parallelogram. Two
Aristotle
the foremost Greek scientist, studied motion and divided it into two types: natural and violent motion. Natural motion � thought to be straight up or down, objects would seek their natural resting place, natural for heavy things to fall, light things to r
Nicolaus Copernicus
moving earth idea, resoned that the simplest way to interpret astronomical observations was to assume that Earth and the other planets move around the sun, earth was believed to be at center of the universe at the time suggested the idea of a moving earth
Friction
name given to the force that acts between materials that touch as the move past each other, caused by irregularities in the surfaces of objects that are touching, if absent a moving object would need no force whatever to remain in motion, reacts in the op
acceleration
possible for acceleration to be going in one direction and object moving in the opposite...deceleration, the rate at which velocity is changing, calculated velocity divided by time , whenever there is a change in motion/velocity, or direction, measured in
Galileo
argued that only when friction is present�as it usually is�is a force needed to keep an object moving, ball rolling down hill speeds up and a ball rolling up hill, opposed by gravity slows down, a ball on level surface does not speed up or slow down, it h
Inertia
tendency of a moving body to keep moving is natural and that every object resists change to its state of motion property of a body to resist changes to its state of motion, amount depends on mass, the more mass an object has the greater its inertia and th
Newton's first law
law of inertia, restatement of Galileo's idea that a force is not needed to keep an object moving. States that every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero net force. Objects at rest stay
mass
the amount of material present in the object, is the measure of inertia of an object that an object exhibits in response to any effort made to start it, stop it, or change its state of motion, measured in kilograms, not weight, depends only on the number
Newton
unit of force, saw moving things required no force to keep moving if friction was not present
relative
an object is moving if its position relative to a fixed point is changing, earth moves relative to the sun a car to the track
speed
how fast an object it moving (velocity), first measured by Galileo as the distance covered and the time it takes, calculated by the distance divided by time (V=d/t), miles per hour, lightyears per century, kilometers per hour, centimeters per day, 60km/h,
instantaneous speed
the speed at any instant, a car doesn't always move at same speed, maybe at that speed for one minute but slowing down and speeding up varies the speed, indicated by the speedometer, instantaneous speed is equal to the acceleration x elapsed time, v = spe
average speed
total distance covered divided by the time
Velocity
a speed in given direction, 60, km/h north, how fast an object moves, velocity is how fast and in what direction, constant velocity, steady speed�straight line, in order to maintain constant velocity, a car must maintain its direction and speed, traveling
freefall
object moving under the influence of gravitational force only, affected on by gravity, acceleration of object in free fall is about 10 meters per second squared, g = acceleration, object in free fall falls 10 meters each second, 0-0, 1-5, 2-20, 3-45, 4-80
elapsed time
the time that has elapsed, or passed, since the beginning of any motion
at peak
instantaneous speed is zero, velocity is zero, acceleration is 9.8m/s/s, speed decreases the same as it increases,
time vs. speed graph
independent on x-axis, time, dependent on y-axis time, slope represents acceleration, straight diagonal line represents constant speed,
distance vs. time graph
curved line up shows increase in speed or acceleration
Air resistance
drop a coin and feather outdoors and the coin reached the ground first, less surface area, in a closed vacuum they both would hit the ground first because air resistance is negligible only affected by 9.8 acceleration of gravity, noticeably slows the moti
hang time
can be calculated using the formula d = 1/2gt-squared which is also, t = 2d/g inside a square root
Scalar addition, subtraction, multiplied, or divided
only magnitude is added, may be adding sand to bags or an airplane traveling, use pythagoream thyrm...pg 70-71, traveling at 80km/h, now flies into the wind or against a 20km/h wind 80km/h - 20km/h = 60 km/h, in the case of adding a pair of equal magnitdu
components
two vectors at right angles that add up to a given vector are known as components of the given vector the replace,
resolution
the process of determining components, the perpendicular components of a vector are independent of each other
projectile
a cannonball shot from cannon, stone thrown into air, ball rolling off the edge of table, spacecraft circling earth are all projectiles, any object that moves through air or space, acted on only by gravity, and air resistance if it is present.(ball rollin
inversely
the two values change opposite direction. As the denominator increases, the whole quantity decreases by the same factor
Newton's second law
the acceleraiton produced by a net force is directly proportional to the magnitdue of the net force, is in the same direction the net force, and is inversely proportional to the mass of the object � acceleration~ net force/mass � newtons net force, kilogr
fluids
liquids and gases, other form of friction rather than just solids, an object pushes aside the fluid this is friction, slower speeds are reached in water than air
free-body diagram
a diagram showing all the force on an object....USE IT!
pressure
no matter how a book is placed on table, force is the same and pressure changes, weight is always the same, depends on area of contact, for a constant force, an increase in the area of contact will result in a decrease in the pressure, the amount of force
pascals
measure for pressure, newtons per square meter (Pa), one newton per square meter is equal to one pascal
terminal speed
the speed at which the acceleration of a falling object is zero because friction balances the weight, the net force on the object is zero and it stops accelerating, heavier objects fall faster until they reach terminal speed, for a sky diver is 150-200 km
terminal velocity
terminal speed together with the direction of motion
physics
the study of the processes of motion and force, and how these concepts/elements interact with matter throughout the universe.
Newton's third law of motion
For every force, there is an equal and opposite force, describes the relationship between two forces in an interaction, states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first ob
interaction
a mutual action is an INTERACTION between on thing and another. The hammer pushes down on the nail, the nail pushes back on the hammer. All consist of a reaction force and action force...a given force exerted on a small mass produces a greater acceleratio
action-reaction forces
The hammer pushes down on the nail, the nail pushes back on the hammer. All consist of a reaction force and action force...one would not exist without the other...equal in magnitude and opposite in direction...occur in pairs. To clearly identify these for
Tug-of-war
The only way a team can win tug-of-war is not whether one team can pull more mass than the other, but whether one team can push more on the floor than the other team because the two teams pulling against each other pull with the same force just in opposit
Punching a wall
you cannot hit the wall any harder than the wall hit you. For every interaction between things, there is always a pair of oppositely directed forces that are equal in strength. If you touch another person, that another person touches back on you
momentum
conserved for all collisions as long as external forces don't interfere, the mass of an object multiplied by its velocity, a moving object can have a large momentum if it has a large mass, a high speed, or both, if a truck has more momentum than a car, th
impulse
change in momentum" Because force changes acceleration, the greater force acting on object, the greater change in velocity, the greater change in momentum. The change in momentum depends on the force that acts and the length of time it acts. Like in cras
bouncing
Impulses are greater when when an object bounces. flower pot on head...if bounces on head will hurt more than if breaks. The impulse required to bring an object to stop and then to "throw it back again" is greater than the impulse required merely to bring
Law of Conservation of momentum
Like to accelerate an object, a net force must be applied to it....then...If momentum must be changed, exert an impulse on it. Only can be done externally, air inside basketball or pushing on dashboard will not move the object. If no outside force present
Elastic collisions
Momentum may be transferred from one ball to another in billiards, initial velocity is equal to away velocity of the other ball. Elastic collision is when objects collide without being permanently deformed and without generating heat. Objects bounce
Inelastic collisions
A collision in which the objects become distorted and generate heat. Objects may be tangled as with cars, or couple together as done with trains (net mvbefore = net mvafter) Space vehicles docking in orbit have the same net momentum, just before and just
momentum vectors
The vector sum of the momenta is the same before and after a collision. Even at different angles momentum is conserved...use parallelogram rules.
Collisions
Whenever objects collide in the absence of external forces, the net momentum of both objects before the collision equals the net momentum of both objects after the collision.
Work
the product of the net force on an object and the distance through which the object is moved; work is displacement or we do work when we lift a load against Earth's gravity; quantity/net force x distance; units is the Newton meter (N-m) also called the Jo
Power
How fast the work is done; the rate at which work is done; equals the amount of work done divided by the time interval during which the work is done; the unit of power is the joule per second or the watt; (James watt-18th century developer of the steam en
Energy
The property of an object or system that enables it to do work is energy; measure in joules; something has to happen in order for the object to do work, like a compression of atoms or spring;
Mechanical energy
the energy due to the position of something or the movement of something; two forms include kinetic Energy (KE) and Potential Energy (PE)
Potential Energy
Energy that is stored and held in readiness, that is because in the stored state it has the potential to do work; stationary object is one example; elastic potential energy, chemical energy, and gravitational potential energy
Elastic Potential energy
stretched or compressed spring; a bow is drawn back, energy is stored in the bow, bow does work on arrow; a stretched rubber band has potential because of position, like a slingshot is capable of doing work
Chemical Energy
fuels; chemical change takes place, the electric charges within and between molecules are altered; potential energy found in fossil fuels, electric batteries and the food we eat
Gravitational Potential Energy
work is required to elevate objects; water in elevated reservoir and the raised ram of a pile driver; Work = fxd; PE = mgh
Kinetic Energy
KE = 1/2mv^2; energy of motion; if the object is moving, thin it is capable of doing work; the kinetic energy of a moving object is equal to the work required to bring it to its speed from rest, or the work the object can do while being brought to rest --
Work-energy theorem
describes the relationship between work and energy; states that whenever work is done, energy changes; Work = ?KE; if no change in KE then work is not done
law of conservation of energy
the study of various forms of energy and the transformations from one form into another is the law of conservation of energy; The law of conservation of energy states that energy cannot be created or destroyed. It can be transformed from one form into ano
machine
a device used to accomplish work or make work easier; a device used to multiply forces or simply to change the direction of forces; a machine cannot put out more any more energy than what is put in; a machine cannot create energy; a machine transfers ener
lever
a simple machine made of a bar that turns about a fixed point; work input = work output; a simple machine made of a bar that turns about a fixed point; other machines include inclined plane, pulley, wheel and axle, wedge, and screw; can multiply forces bu
fulcrum
the pivot point;
mechanical advantage
the ratio of output fore to input force; includes ideal - what it should be and actual - what it really is
pulley
a kind of lever that can be used to change the direction of force; may change the direction or multiply the force or both;
axis
ex. ice skater doing a pirouette turn and a ferris wheel turn around an axis; the straight line around which rotation takes place
rotation
first type of circular motion; object turns about an internal axis - axis located within the body of the object; (spin)
revolution
second type of circular motion; an object turns about an external axis - even though a ferris wheel itself rotates, the riders revolve around its axis; ex. earth rotates around its axis passing through its geographical poles once every 24 hrs. and revolve
Speed (3 types)
linear speed, tangential speed, rotational speed
linear speed
the distance traveled per unit of time; most common form of speed; ex. merry-go-round or turntable, a point on the outer edge travels a greater distance in complete rotation that a point near the center; the linear speed is greater in the outer edge than
tangential speed
speed of something moving along a circular path because the direction of motion is always tangent to the circle; used along with linear speed interchangeably; tangential speed ~ radial distance x rotational speed _ v~rw (w is Mayguh); you move faster if t
rotational speed
AKA angular speed; number of rotations per unit of time; all parts of a merry-go-round or table rotate around their axis in the same amount of time; have the same rate of rotation or same number of rotation per unit of time (RPM's) - phonograph turntables
Train Wheels
ex. (two cups tapeped together at the mouth and put on two yard sticks) like a tapered cup rolls in a curve because the wide part of the cup rolls faster than the narrow part, like a cup the "wheels" tend to center themselves whenever they attempt to roll
centripetal acceleration
any object moving in a circle undergoes an acceleration that is directed towards; if object travels in circle then its velocity and direction is changing so it is accelerating
centripetal force
centripetal means "toward the center"; the force directed toward a fixed center that causes an object to follow a circular path; acted on anything moving in a circular path; orbiting electron around a nucleus in an atom from electrical forces, the moon ar
centrifugal force
the apparent outward force on a rotating or revolving body; means "center-fleeing" or "away form the center"; a can attached to a string, when the string breaks the can moves not directly outward in a straight line from the center but tangent to its circu
torque
produced by turning force and tends to produce rotational acceleration; ex. a doorknob, turn on facet, or tighten a nut with a wrench; different from force; must apply force to create torque; to make an object turn or rotate, apply a torque which produces
lever arm
the distance from the turning axis to the point of contact; torque equals force times lever arm or distance; increase the lever arm, greater the torque even thought the applied forces may be the same the torque can be increased by just changing the length
center of mass
where all the mass of an object is considered to be concentrated but this doesn't mean that both sides will have equal mass; in an object it is the point located at the objects average position of mass; a spinning pall and bat always follow a parabolic cu
rotational inertia
the greater an object's rotational inertia, the more difficult it is to change the rotational speed of the object; when you run, you bend your legs to reduce rotational inertia; for similar mass distribution, short legs have less rotational inertia than l
longitudinal axis
head to feet, ice skater moves about this axis when going into spins
transverse axis
front to back
medial axis
left to right
MOMENTUM + rotation
three types - linear, angular and rotational velocity
linear momentum
the product of mass and velocity
angular momentum
ex. gyroscope; defined as the product of rotational inertia and rotational velocity
rotational velocity
when a direction is applied to velocity; magnitude is rotational speed
law of conservation of angular momentum
states that if no unbalanced external torque acts on a rotating system, the angular momentum of that system is constant; angular momentum is conserved when no net external torque acts on an object