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  • classical mechanics

    describes the relationship between the motion of objects in our everyday world and the forces acting on them

    force

    a push or pull

    vector

    force is a __________ quantity.

    contact force

    touching

    field force

    gravity, charges, magnets

    1. Strong nuclear force
    2. Electromagnetic force
    3. Weak nuclear force
    4. Gravity

    What are the four fundamental forces of nature (field)?

    strong nuclear force

    strongest force; attractive force that holds the nuclei of atoms together.

    electromagnetic force

    long-ranged but weak; attractive or repulsive force between objects carrying electrical charge.

    weak nuclear force

    very short range and very weak; responsible for radioactive decay.

    gravity

    always attractive, and acts between all matter in the Universe; weak, but very long ranged; it's the dominant force in the universe for shaping galaxies and stars.

    inertia

    the tendency of an object to continue in its original motion (or resist change in motion)

    mass

    __________ is a measure of inertia

    scalar

    inertia is a ___________ quantity

    kg

    SI units for inertia are _____

    Newton's First Law of Motion: Law of Inertia

    an object at rest stays at rest and object in motion stays in motion unless acted upon by a net external force.

    net force

    the sum of all forces on an object

    1st law implications

    1. Space objects will move forever once set in motion.
    2. Friction and air resistance are the net forces that usually slow objects.

    Newton's Second Law of Motion

    F=ma
    If a constant force is applied to an object,
    it will ACCELERATE

    NO

    If ΣF (net force) = 0, then there is
    _______ ACCELERATION.

    newtons

    force units are measured in ____________

    weight

    the gravitational pull on an object; always points straight down

    W=mg

    weight equation

    universal; location

    mass is ____________; weight depends upon the ___________.

    Newton's Third Law of Motion

    1. Every action has an equal and opposite reaction
    2. Forces always occur in pairs
    3. Action and reaction forces must occur on 2 separate objects
    4. Equal in magnitude but opposite in direction

    free body diagram

    a drawing showing all forces on an object

    normal force

    force of surface on object
    1.Perpendicular to surface
    2. Acts opposite to gravity

    tension

    force on a rope

    same

    the tension on a rope is the __________ at all points on the rope.

    conculsions of the force table demo

    1.Balancing forces involves vector addition.
    2.The sum of the forces involves considering x- and y-direction forces.
    3.Objects in equilibrium have their forces balanced in both x- and y- directions.

    equilibrium

    Means ΣF = 0
    there is no acceleration.
    (there must be no net torque too)

    static equilibrium

    not moving; a=0

    dynamic equilibrium

    constant velocity; a=0

    Assumptions with Newton's Laws

    Objects behave as particles
    Masses of strings are negligible
    Interested only in the forces acting on the object
    (neglect reaction forces)

    friction

    resistance to motion

    surface imperfections and intermolecular forces

    friction is caused by......

    1.surface material
    2. normal force of each surface on the other

    factors of friction

    force of friction (f)

    The direction of the f is opposite the direction of motion
    Friction is proportional to the normal n
    f = µ n (fyi 0 < μ < 1)

    greater

    static friction (fs) is ___________ than kinetic friction(fk)

    types

    µ depends on the _________ of surfaces in contact

    independent

    The µs and µk are _____________ of the area of contact

    static friction

    acts to keep the object from moving; if Fa increases, so does ƒs

    kinetic friction

    acts when the object is in motion; f is constant while in motion

    inclined planes

    *Set the x-axis along the incline and y-axis perpendicular to the incline
    *Normal points along y-axis
    *Weight points straight down (break into components)
    *Friction acts along x-axis

    upward

    objects accelerating _________ seem heavier.

    downward

    objects accelerating ___________ seem lighter.

    floor

    ________ scales display the normal force; they are they are the same when a=0.

    Weight down and Drag/Air Resistance up

    falling objects have 2 forces on them: What are they?

    constant

    objects don't accelerate downward forever - at some point their velocity becomes _____________.

    0

    When the upward Fair resistance = the downward Fgravity, the Fnet = ____.

    terminal velocity

    constant speed

    geometry

    an object's terminal velocity depends on the object's _____________.

    fun fact

    a human's terminal velocity is about 150 mph; an ant's is so low that it can fall far and not get hurt.

    hydrostatics

    non-moving fluids (ex. pressure, floating)

    fluid

    a gas or liquid (both flow)

    pressure

    a force pushing against a specific area of a surface. (force/area)

    atmospheric pressure

    caused by 100 km of air above us

    pressure and depth

    the force exerted by a fluid depends on the height of fluid above it; the deeper the object, the more pressure.

    buoyant force

    acts upward on an object in a fluid making an object feel lighter.

    Archimedes Principal

    The buoyant force on an object equals the weight of water displaced by the object.

    apparent weight

    your weight in water
    (it's less than your weight in air because FB pushes upward)

    buoyant force and the weight

    Whether an object sinks or floats depends on the .........

    upward

    If the object is less dense than the fluid,
    the object experiences a net _____________ force

    downward, downward

    If the object is more dense than the fluid:
    The net force is ______________, so
    The object accelerates _________________

    sinks

    If an object's weight > buoyant force, then it ________.

    floats

    If an object's weight < buoyant force, then it _______.

    floating object

    *The object is in static equilibrium
    *The upward buoyant force is balanced by the downward force of gravity

    force pump

    moves fluid by changing the pressure in the fluid

    Pascal's Principle

    When you apply a force to a confined fluid (a closed system), that pressure is applied equally to all parts of the fluid

    hydraulics

    Pressure is transferred through a fluid.
    An applied small Force on a small Area transmits a big Force on a big Area.
    Ex: car brakes, car lift

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