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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.

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

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

(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

Example: