Speed
The rate at which an object moves
Velocity
The combination of speed and direction
Acceleration
The rate at which an object’s velocity changes (either in speed OR direction OR both)
M/s^ 2
Acceleration caused by gravity
~ 9.8 m/s^2
Acceleration of a falling object = acceleration of gravity — УСКОРЕНИЕ СИЛЫ ТЯЖЕСТИ
Gravity accelerates all,objects by the same amount, regardless of their mass
(On Earth air resistance cause the difference. But on the Moon, for example, objects will fall at the same rate)
WHY?
Heavier objects experience more gravity force but at the same time more inertia (resist more)
|==» Gravitational mass= inertial mass
(How strongly gravity pulls an object) (How much an object resist acceleration)
Momentum
The product of an object’s mass and velocity
p = m*v p - ИМПУЛЬС Показывает как тяжело изменить движение тела (acceleration)
———————————-
NB: интенция ❌ = ❌импульс —> инерция** - св-во // импульс - физ величина
** - св-во тел сохранять состояние покоя или равномерное движение до влияния внешних сил
Force
Anything that can cause a change in momentum
(Физ величина, характеризующая меру воздействия одного тела на другое)
Measured in Newtons = kg*(m/s^2)
Net force
An overall force to which an object responds
= to the rate of change in the object’s momentum OR <=> R = m*a - the sum of all individual forces
———————————
РАВНОДЕЙСТВУЮЩАЯ сила
- сила, которая производил на тело такое же действие, как и несколько одновременно действующих на него сил <=> R=F1+F2+…Fn
———————————
R=0 в состоянии покоя ИЛИ при постоянной V
II==» b/c any forces acting on the object, like friction or air resistance, are perfectly balanced by other forces, such as the force generated by an engine
Mass AND Weight
Mass - const - the amount of matter on an object
——
Weight - can vary - the net force that an object applies to it surroundings
(In the stationary body it’s = m*acceleration of gravity)
Depends on m and forces acting on your m (including gravity)
Free-fall
The condition in which an objects falling without any resistance
At free-fall objects are weightless WEIGHT=0
In fact, you are in free-fall whenever there’s nothing to prevent you from falling
F.e., astronauts and spaceships orbiting Earth are constantly falling (in free-fall basically).
Они как бы все время падают по прямой, но гравитация их «закручивает»
—»
ускорение свободного падения=центростремительное ускорение
How did Newton change our view of the universe?
He showed that the same physical laws that operate on Earth also operate in heavens
B/c previously it was thought that heavens were totally distinct from Earth so physical laws on Earth did not apply to heavenly motion (by Aristotle)
II==» Newton eliminated Aristotle’s distinction between two realms and brought the heavens and Earth together in one universe
(The birth of astrophysics)
Newton’s 1st law of motion
An object moves at constant velocity unless a net force acts to change its speed or direction
———————
=ЗАКОН ИНЕРЦИИ
Если на тело не действуют силы или их действие сконпенсировано, то данное тело находится в состоянии покоя и равномерного прямолинейного движения
V= const IF F=0
Newton’s 2nd law
Force= m*a
Чем больше сила, тем меньше ускорение тела
При ⬆️m, a⬇️
(Related questions: 1) throwing baseball; 2) effect of larger planets on celestial objects VS the ones of smaller’
Закон всемирного тяготения
Fg=G(m1*m2)/r^2
Why you can throw a baseball faster than you can throw a shot (ядро (для метания))?
The F your arm implied to both baseball and the shot = m*a
B/c the m(shot) > the m(ball), the same F from your arm gives the shot smaller acceleration.
B/c of the smaller acceleration, the shot leaves your hand with smaller speed ==» it travels a shorter distance before hitting the ground
Astronomical application of N’s 2nd law
Explains why larger planets (f.e., Jupiter) have greater effect on asteroids and comets than smaller planets (f.e., Earth)
Mj > Me => J. exerts more gravitational force on passing asteroids/ comets than smaller ==> sends them scattering with greater acceleration
(-> F=m(const)*a)
Newton’s 3rd law of motion
For any force there is always an equal or opposite reaction force
==»
Objects always attract each other through gravity
—————
ЗАКОН РАВЕНСТВА ДЕЙСТВИЯ И ПРОТИВОДЕЙСТВИЯ
F равны по модулю, противоположны по направлению
—————
F1= -F2
—————
F of Earth ↔️ F of you BUT as M of you < M of Earth, your acc. should be much (much) > acc. of Earth ==»
II==» that’s why you fall towards Earth and not visa verse
Conservation of momentum
————
ЗАКОН СОХРАНЕНИЯ ИМПУЛЬСА
————
“The total momentum of a system remains constant unless acted upon by an external force”
————
В замкнутых системах// при уравновешенных силах
————
Исходит из однородности пространства
————
Сумма p(нач)= Сумма p(конеч)
————
Пояснение:
по 3-му закону Ньютона
F1=-F2 —> F1+F2=0 —> изм.Fизм.t=изм.p —> (F1+F2)изм.t=изм.p1+изм.p2 —> 0изм.t=изм.p1=изм.p2 —> (for any ‘’t’’) изм.P1+изм.p2=0 <=> (p1(после)-p1(до))+(p2(после)-p2(до))=0 <=> p1(до)+p2(до)=p1(после)+p2(после)
Ч.Т.Д.
Conservation of angular momentum
ЗАКОН СОХРАНЕНИЯ МОМЕНТА ИМПУЛЬСА
(Про вращательное движение)
—————
“Ten principe that in the absence of net torque (twisting force) the total angular momentum remains constant”
—————
L= const = I* w =vmr (I - Inertia; w - angular velocity) (kg*m^2)/s
—————
Conservation of Energy
ЗАКОН СОХРАНЕНИЯ ЭНЕРГИИ
————
“Energy cannot be created or destroyed, it can be only transferred or transformed in other types of energy
————
E(механич)= const =Е(кинетич) + Е(потенциал) E(кинетич)1+Е(потенциал)1=Е(кинетич)2+Е(потенциал)2
Types of energy
1) Kinetic (motion) — energy of motion (in joules (Дж))
|
thermal kinetic energy
(For 1) and 3) ): ⬆️Gr.Ep ⬇️Ek
2) radiative (light) — energy carried by light
3) potential (stored) — energy stored for later conversion into kinetic or radiative energy
| | | |
Gravitational pot.en. Chemical pot.en. Electrical pot.en. **Pot.en. of mass*u
Gravitational potential energy
Energy that an object has blue virtue of its position in a gravitational field
⬆️the distance that an object can potentially fall —> ⬆️ the gravitational pot.en.
—————
(Related topic: explains the process of the formation of stars)
The F formation of stars
Before the process begins its matter is spread out in a large cloud of gas. Most individuals particales are far from the center of a cloud => Gr.Ep is ⬆️ —»
—» As the cloud shrinks under its own gravity, dist.⬇️ => Grav.Ep⬇️ —»
—» this “lost” potential energy gets converted into thermal energy, making the center of a cloud hot —» nuclear fusion —» 💥 etc
Thermal energy
Is the collective kinetic energy, as measured by t, of many individual particles moving within a substance
———
ТЕПЛОВАЯ ЭНЕРГИЯ
———
Depends on —> t; Density; The number of particles
———
Measured in Kelvin’s
Mass-energy
-mass itself is a form of potential energy (Ep) that can be converted into other forms of energy under certain conditions
_________________
II==» mass and energy are 2 forms of the same thing
_________________
Energy 🔁 mass
Ep=m*c^2 (c - speed of light) ==»> small amount of m contains gauge amount of energy (pot.)
