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basic year 8 science knowledge > physics > Flashcards

physics Flashcards

1
Q

Што е сила

A

СИла е физичка величина која го опишува взаемното дејствување на две тела. Сила=F
Force happens when two bodies interact.

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2
Q

Како се поделени силите според нивното дејство?

A

Сила за туркање,
сила за влечење,
сила за растегнување
и сила за завртување

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3
Q

Видови сила според нивната природа

A

електрична сила,
магнетна сила,
еластична сила,
Земјина тежа,
гравитациона сила,
сила на триење,
потисна сила

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4
Q

Мерна единица за сила?

A

Њутн (N) 1MN=1 000 000 N
1KN= 1000N

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5
Q

Со што мериме сила

A

Со динамометар

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6
Q

Што е еластична сила

A

силата на пружината под чие дејство таа се враќа во нејзината првобитна состојба

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7
Q

Од што зависи големината на еластичната сила?

A

од тежината која ја обесуваме на пружината

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8
Q

Хуков закон?

A

F=-k*x
F-јачина на еластична сила
k-константа на истегнување
x-издолжување на пружината

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9
Q

Што е механичко движење

A

Промената на положбата на едно тело во однос на другите тела

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10
Q

Што е изминат пат

A

Делот од траекторијата (линија што ја опишува тело кога се движи) што телото го поминува за одредено време

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11
Q

Што е брзина

A

Физичка величина која кажува колку бргу се движи телото. V=S/t

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12
Q

Мерна единица за брзина

A

m/s
km/h

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13
Q

Какви физички величини се силата и брзината

A

Векторски, имаат правец, насока и големина

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14
Q

Какви можат да бидат движењата според брзината uniform vs non-uniform motion

A

Рамномерни (брзината не се менува)
Нерамномерни (брзината се менува)

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15
Q

Што е забрзување?

A

Забрзување е промена на брзината во единица време. а=забрзување

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16
Q

Пресметување на забрзување?

A

a= v2-v2/t2-t1

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17
Q

Мерна единица за забрзување

A

m/s^2

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18
Q

Њутнови закони?

A

1-Закон за инерција
2-F=m*a
3-Закон за акција и реакција

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19
Q

Прв Њутнов закон?

A

Закон за инерција: Секое тело останува во состојба на мирување или релативно движење се додека некое друго тело не ја промени таа негова состојба.

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20
Q

Втор Њутнов закон

A

Силата што дејствува врз телото е еднаква на производот помеѓу масата на телото и неговото забрзување под дејство на таа сила.
F=m*a

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21
Q

Трет Њутнов закон?

A

Две тела заемно си дејствуваат со сили што се во исти правец, спротивна насока но еднакви по големина

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22
Q

Што е сила на триење?

A

СИла која се јавува кога две тела се допираат или се движат едно во однос на друго

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23
Q

Каква е насоката на силата на триење

A

Секогаш спротивна од телото кое се движи

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24
Q

Пресметување сила на триење

A

Ftr=M * Fn
Ftr- сила на триење
M- коефициент на триење
Fn- нормална сила

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25
Q

Што е Земјина тежа?

A

Силата со која Земјата ги привлекува сите тела што се наоѓаат на нејзината површина

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26
Q

Што е маса?

A

Мерка за инертноста на телото

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27
Q

Што е тежина

A

Силата со која телото дејствува на подлогата или на местото на кое е обесено G-тежина

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28
Q

Пресметување тежина на телото?

A

G=m*g
g=9.81 Земјино забрзување

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29
Q

Што е сила на отпорот на воздухот?

A

Нагорната сила што дејствува врз падобранот е сила на отпорот на воздухот

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30
Q

Што е енергија?

A

Способноста на телото да врши работа

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31
Q

Мерна единица за енергија

A

1 Ј- џул

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32
Q

Што е работа

A

СОвладување отпор (сила) на извесна оддаелеченост. А-работа

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33
Q

Пресметување на работата

A

А=F*S

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34
Q

Како се пренесува енергијата?

A

-електрицитет
-со звук
- со зрачење

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35
Q

Гравитационо потенцијална енергија?

A

Енергија на тело подигнато на висина од Земјата

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36
Q

Пресметување гравитационо потенцијална енергија

A

Ep=m * g * h

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37
Q

Пресметување кинетичка енергија?

A

Ek=m * V^2 /2

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38
Q

Каде се се создава електрична енергија?

A

Хидроцентрала, термоцентрала, нуклеарна централа, гасна централа, фото-волтаични ќелии

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39
Q

Што е генератор

A

Направа која механичката работа ја претвара во електрична енергија

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40
Q

Што е е електромотор

A

Направа која електричната енергија ја претвара во механичка работа

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41
Q

Што е рефлексија на светлината

A

Појава на одбивање на светлината од предметите

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42
Q

Што е транспаренција

A

Појава на пропуштање на светлинаата низ предметитет

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43
Q

Што е апсорпција

A

Појава на впивање на светлината во предметите

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44
Q

Како се формираат сенките

A

Кога светлината се блокира

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45
Q

Што е полусенка?

A

Кога имаме поголем светлински извор и кога осветлуваме со него непровидно тело, освен сенка имаме дел кој делумно е осветлен

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46
Q

Затемнување на Сонцето?

A

Кога во иста линија се подредени Сонцето, Месечината и Земјата (месечина во средина) Сонцето ја осветлува месечината и таа фрла сенка на Земјата. Во тој дел има затемнување на Сонцето. Каде се фрла полусенка е делумно затемнување

47
Q

Затемнување на Месечината

A

Кога се подредени Сонцето, Земјата, Месечината Сонцето ја осветлува Земјата и таа фрла сенка на месечината.

48
Q

Што е светлосна година

A

Растојанието што го поминува светлината за време од една година

49
Q

Брзина на светлината, и за колку време патува до Земјата

A

300 000 км/с за 8,3 мин

50
Q

Закон за рефлексија на светлината

A

Упадниот агол=агол на рефлексија

51
Q

Што е рефракција на светлината?

A

Појава на менување на правецот на простирање на светлината на гранична линија помеѓу две оптички површини

52
Q

Закон за прекршување на светлината во трите случаи

A

помала густина –> поголема густина
влезен агол >агол на прекршување

поголема густина –> помала густина
влезен агол<агол на прекршување

53
Q

Причина на прекршување на светлината кога минува од една во друго оптичка срединс

A

Причината епромената на брзината на светлината

54
Q

Индекс на прекршување на светлината?

A

n=A/B
A-упаден агол
B-агол на прекршување
n=C1/C2
С1-брзина на светлина во прва средина
С2-брзина на светлина во втора средина

55
Q

Што е дисперзија на светлината

A

Разложување на светлината на нејзините составни бои

56
Q

Што е стаклена призма

A

Тело кое има способност да ја разложи светлината на составните бои

57
Q

Бои на белата светлина?

A

Црвена, портокалова, жолтам зелена, сина, темносина, виолетова

58
Q

Спектрални основни бои и Адитивно мешање бои?

A

црвена, зелена и сина.
Адитивно мешање бои = две основни спектрални

59
Q

Основни пигментски бои и суптрактивно мешање бои

A

црвена, жолта сина
суптрактивно мешање бои=трите основни пигментски се добива црна

59
Q

Што е Земјина оска

A

Права линија која ги поврзува Северниот и Јужниот пол

60
Q

Што е Земјина револуција

A

Вртење на Земјата околу Сонцето во период од 365 дена и 6 часа

61
Q

карпести и гасовити планети?

A

Меркур, Венера, Земја, Марс-карпести
Јупитер, Сатурн, Уран, Нептун-гасовити

62
Q

What does force do to the objects

A

Force can Change the Shape and Size of an Object
Force can Change the direction of an Object
Force can Change the Speed of an Object
Force can change the state of Rest or Motion of an Object

63
Q
A
64
Q

types of motion

A

Linear:
Rotational: axis
Circular: `
Vibratory: guitar strings

65
Q

scalar quantities vs. vector quantities

A

Quantities that depend on magnitude (value) and not on direction are scalar
ex. you say you travelled 25km from your home to Delhi

Quantities that consider magnitude and direction are vector and are represented by putting an arrow on their symbol
ex. You say you travelled 25km east from your home to Delhi

66
Q

distance vs. displacement

A

The magnitude of the length enclosed by a moving entity is called distance. It has no direction.

(izminat pat) Displacement is the shortest distance between two points or the distance between the starting and final positions concerning time. It has magnitude as well direction.
Displacement can be zero, but distance cannot.
https://selftution.com/wp-content/uploads/2020/04/Selftution-Difference-between-distance-and-displacement-vector-and-scalar-quantities.jpg

Distance is the measure of “how much ground an object has covered during its motion” while displacement refers to the measure of “how far out of place is an object.”

think of triangle ABC

67
Q

what is magnitude

A

The size or extent of a physical quantity is magnitude. In physics, we have scalar and vector quantities. Scalar quantities are only expressed as magnitude. E.g: time, distance, mass, temperature, area, volume.

Vector quantities are articulated in magnitude as well as the direction of the entity. E.g: Velocity, displacement, weight, momentum, force, acceleration, etc.

68
Q

velocity vs. speed

A

speed-scalar
Speed is the time rate at which an object is moving along a path
speed=pat/vreme
speed=distance/time

velocity-vector
while velocity is the rate and direction of an object’s movement
velocity=IZMINAT pat/vreme
velocity=displacement/time

69
Q

reference point

A

Телото во однос на кое се движат другите тела
ex. Let us consider a car standing in front of the house. Let’s say primarily it is at location A then after some time, it moves to location B. That means it has changed its position concerning the stationary object that is the house.
ex. To explain the position of an object we require a reference point or origin. An object may appear to be moving to one observer and stationary to another.
Example: A traveller inside a bus sees the other passengers be at rest, whereas a spectator outside the bus sees the passengers are in motion.

70
Q

distance-time graph

A

Distance-Time graphs show the change in position of an object for time.
https://media.geeksforgeeks.org/wp-content/uploads/20210226132738/2.jpg
As the slope is constant OA implies uniform motion with constant speed.
AB implies the body is at rest as the slope is zero
B to C is non-uniform motion

71
Q

uniform vs. non-uniform motion

A

When an object covers the same distances in the same intervals of time it is in uniform motion. An entity said to be in non-uniform motion when it covers unequal distances in equal intervals of time.

72
Q

velocity-time graphs

A

Velocity-Time graphs show the change in velocity concerning time.
https://media.geeksforgeeks.org/wp-content/uploads/20210226132740/3.jpg
Slope gives acceleration
Line parallel to x-axis implies constant velocity.

73
Q

when were newton’s laws proposed

A

late 17th century

74
Q

inertia

A

inertia is a body’s tendency to resist a change in its condition of rest or uniform motion. Inertia is the quality of objects that allows them to remain at rest or, if moving, to continue traveling in a straight line.

75
Q

mass

A

We can define mass as the measure of the amount of matter in a body.
scalar

76
Q

how inertia and mass are related

A

Inertia and mass are dependent upon each other. The mass is directly proportional to its inertia, the more the mass of the body more will be its inertia, and hence, more will be the force required to change its state of motion.

Some examples to learn inertia are:

A cricket ball has higher inertia than a rubber ball, it takes a great deal of force to change its direction.

77
Q

why we fall forward when buses stop

A

Because the lower half of our body is in contact with the ground, any forces operating on the bus’s base will be sensed by our lower half, which will react correspondingly. The upper half of our bodies, on the other hand, is not in contact with any portion of the vehicle. As a result, as the bus comes to a halt, the lower half of the body comes to a halt while the upper half continues to move, causing us to fall forward. We also tumble backwards when the bus suddenly starts.

78
Q

what is momentum

A

The momentum of a body is the product of the mass of the body and its associated velocity. Momentum can be considered to be a vector quantity, that is, it has both an associated magnitude and direction.
p= m × v

79
Q

newton’s second law of motion

A

It says that for an object under the influence of unbalanced forces, the acceleration of the object is directly proportional to the force applied. In other words, we can say that for a constant mass, the rate of change of momentum is directly proportional to the force applied.

80
Q

ex of newton’s second law of motion athlete and matress

A

A sand bed or cushioned bed is provided to athletes performing long jumps to induce a delay in the change of momentum. The momentum induced because of the velocity and mass of the athlete is reduced to zero as soon as the athlete reaches back on the surface. In case the rate of momentum changes instantly, it may hurt the player. The purpose of the cushioned bed is to delay the momentum of the athlete to zero and thus prevent injury.

81
Q

example for newton’s second law of motion, football bsall

A

Kicking a football changes its direction and also changes its velocity. It can increase or decrease the velocity of football. The force applied by the footballer is responsible for the change that the ball produces. Thus, Newton’s Second Law of Motion also holds true in this case.

82
Q

newton’s third law of motion

A

The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object.
“To every action there’s always equal and opposite raction.”

83
Q

universal law of gravitation

A

Every object in the universe attract every other object by a force which is directly proportional to product of masses of both objects and inversely proportional to square of the distance in between them

84
Q

what does gravitation depend on

A

The gravitational force on the object depends on the mass of the object, the more the mass of the object more will be the force applied to it by the other objects.

85
Q

what is acceleration due to gravity

A

Acceleration due to Gravity is defined as the acceleration attained by an object due to the gravitational force of attraction. When a body is fallen toward the earth it experiences a change in its acceleration due to the gravitational pull (or force) of the Earth.

86
Q

weight

A

The weight of an object is defined as the measure of the amount of force that acts on mass because of the pull of gravity. Weigh is the measure of force. Therefore, Weight will vary depending on the location.

87
Q

weight formula

A

W=m * g
where m is the mass of the object
and g is the acceleration due to gravity

88
Q

can weight be zero?

A

yes, when gravity is zero

89
Q

scientific work vs daily-life work

A

So we can state some conditions for work as follows:

1) A force should act on an object.
2)The object must have some displacement.

If any of the above condition does not occur then work is not done.
so things like studying, or pushing a wall without the wall getting displaced are not work

90
Q

work definition

A

Work done = Force x Displacement

91
Q

how can energy be transferred

A

Mechanically
Electrically
By Radiation
By Heating

92
Q

what is mechanical energy

A

kinetic + potential energy

93
Q

k.e. formula

A

k.e=mv^2/2

94
Q

potential energy

A

Potential energy is energy that has the potential to become another form of energy. Potential energy is defined as the energy stored by an object due to its arrangement, state or position.

95
Q

Law of Conservation of Energy

A

Energy can neither be created nor destroyed but can be transferred from one form to another. It is the law of conservation of energy. The whole energy before and after the alteration remains constant.

96
Q

potential energy formula

A

P.E.=m * g * h
m=mass of body
g= acceleration due to gravity
h= height from earth

97
Q

types of potential energy

A

chemical, gravitational and elastic

98
Q

gravitational potential energy?

A

Gravitational potential energy of an object is defined as the energy possessed by an object that increased to a certain height against gravity.
it depends on the mass of the object and the height at which it is

99
Q

elastic potential energy def and formula

A

Elastic potential energy is the energy that is stored in objects. It can be compressed or stretched such as rubber bands, trampoline, and bungee cords. The object that can stretch more, has more elastic potential energy.

P.E.E=kx^2/2
k-elasticity constant
x-the elongation of the spring

100
Q

what is friction

A

Friction, force that resists the sliding or rolling of one solid object over another. It acts on both the surfaces.

101
Q

factors affecting friction

A

roughness/smoothness of body
roughness/smoothness of surface
shape of object

102
Q

what is reflection

A

The phenomenon, known as “reflection” or “reflection of light,” occurs when a light beam strikes any polished, smooth, or bright object and bounces back to our eyes.

103
Q

law of reflection

A

The incident ray, the reflected ray, and the normal all lie on the same plane.
The angle of incidence (∠i) is always equal to the angle of reflection (∠r).

104
Q

types of reflection

A

regular
diffused - light hits a rough surface, 2nd part of law of reflection isn’t true here

105
Q

what is refraction

A

The bending of a light wave when it passes from one medium to another due to the change in the speed of the light traveling the two different media is called the Refraction of light.

106
Q

types of refraction

A

denser –> rarer medium
rarer –> denser medium
dense medium = smaller angle of refraction/incident
rare medium = bigger angle of refraction/incident

107
Q

examples of light refraction

A

The stars twinkle in the night sky due to the refraction of their light.

The formation of rainbows in the sky and VIBGYOR, when white light passes through the prism are also major examples of refraction.

A swimming pool always seems or looks much shallower than it really is because of the light that comes from the bottom of the pool bends at the surfaces due to the refraction of light.

108
Q

dispersion of light?

A

Dispersion is defined as the spitting of white light into different colors when passed through a prism.

109
Q

colours of white light

A

VIBGYOR

110
Q

how does light dispersion happen

A

When light passes from one medium to another medium speed of propagation of light changes as a result the light is refracted. Now when the light passes through the prism, it gets refracted this refraction of light makes the light split into various colours and this phenomenon is called the dispersion of light through the prism.

111
Q

why does x bend the most and y the least

A

Different colours in the light range have different wavelengths. Therefore, the speed at which they bend varies depending on the wavelength, in which the Violet light bends most, and the Red bends the least.

112
Q

atmospheric refraction

A

Twinkling of stars: As we discussed earlier the temperature of the atmosphere’s layer is different at a different height which creates different media for refraction. Also, the air is not constant which led to a change in temperature and causes refraction. So, when the atmosphere refracts more light to us the star seems bright. However, when the atmosphere refracts less light than the star seems dim, and this process happens so fast that it seems to us twinkling.
Advanced sunrise and Delay in the sunset: Have you ever wondered that the actual sunset happens much earlier than what you usually see? Yes, you heard it right. When we see sunsets, the light ray coming from the sun goes under refraction and bends towards us. At that time, the sun already crossed the horizon. The sun, we see, is an image that is formed due to refraction that is actually higher than its actual position. This results in the delay of sunset and the same thing happen during sunrise which makes it earlier than the actual one.

113
Q
A

basic year 8 science knowledge (2 decks)

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