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National 5: Physics > Unit 3: Dynamics and Space > Flashcards

Unit 3: Dynamics and Space Flashcards

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1
Q

Average Speed

A

Speed recorded over an extended time interval. Given symbol v bar

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2
Q

Instantaneous Speed

A

Speed measured over an extremely short time interval

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3
Q

Scalar

A

Quantity with magnitude only

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4
Q

Vector

A

Quantity with magnitude and direction

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5
Q

Scalar Quantities

A

Speed

Distance

Power

Energy

Mass

Charge

Time

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6
Q

Vector Quantities

A

Velocity

Displacement

Acceleration

Forces

Momentum

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7
Q

Distance

A

Scalar quantity. Total length of the path travelled in any direction

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8
Q

Displacement

A

Length measured in a straight line from the starting point to the finishing point. Direction must also be given

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9
Q

Speed

A

Scalar quantity. Distance travelled in unit time

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10
Q

Velocity

A

Vector quantity. Displacement in unit time (same direction as displacement)

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11
Q

Acceleration

A

Change in velocity per second. Vector. Given symbol a and measured in metres per second per second (ms<strong>-2</strong>)

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12
Q

a =

A

v-u/t

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13
Q

t =

A

v-u/a

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14
Q

v =

A

u + at

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15
Q

u =

A

v - at

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16
Q

V-T Graph - Positive Gradient

A

Straight line sloping upward to the right. Represents a constant acceleration

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17
Q

V-T Graph - Zero Gradient

A

Horizontal Line. Represents zero acceleration

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18
Q

V-T Graph - Negative Gradient

A

Represents a constant deceleration. Straight line sloping downwards

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19
Q

V-T Graph - Area under Graph

A

Equal to total displacement

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20
Q

V-T Graph - Average velocity

A

Calculated using total displacement(s) and time (t). Given symbol v bar

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21
Q

Force

A

Vector Quantity. Given symbol F and measured in Newtons (N)

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22
Q

Forces Can

A

Change the speed of an object

Change object’s direction of travel

Change object’s shape

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23
Q

Friction

A

Force. Always opposes motion and always changes kinetic energy into heat. Present whenever two surfaces are in contact with each other and slide across each other

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24
Q

Weight

A

Gravitational force of attraction acting on an object. Given symbol W and measured in Newtons (N)

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25
Q

Balanced Forces

A

When the forces acting in one direction are exactly equal to forces acting in the opposite direction

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26
Q

Newton’s First Law

A

An object will remain at rest or travel with a constant velocity unless acted on by an unbalanced force

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27
Q

Unbalanced Force

A

Force(s) acting in a particular direction are not cancelled out by force(s) acting in the opposite direction

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28
Q

Newton’s Second Law

A

When an object experiences an unbalanced force it accelerates. The acceleration is proportional to the unbalanced force acting and inversely proportional to the mass of the object

Fun = ma

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29
Q

Newton’s Third Law

A

For every action there is an equal but opposite reaction

If A exerts a force on B then B exerts an equal but opposite force on A

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30
Q

Seatbelts and Forces

A

When a car stops a large frictional force is exerted on the car by the brakes providing a large backwards unbalanced force and according to Newton’s Second Law a large backwards acceleration

Passenger will keep moving at a constant velocity forwards unless a large, unbalanced, backwards force acts on them

Seatbelts provide a backwards unbalanced force

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31
Q

Airbags

A

Increase time taken for head to stop

a = v-u/t so a longer time means a lesser decelaration

Fun=ma (Newton’s 2nd Law) so a smaller acceleration means a smaller force will act on the passengers head

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32
Q

Terminal Velocity

A

When frictional force acting on an objectis equal to the weight and it falls at a constant speed

33
Q

Projectile Motion

A

Defined as the motion in 2 dimensions of an object under the influence of one, constant force

34
Q

Projectiles - Horizontal Motion

A

The motion the ball would have in the absence of gravitational attraction

35
Q

Projectiles - Horizontal Distance

A

Caculated using the formula: d = vh x t

where: d is the horizontal distance travelled (m)

vh is the horizontal speed of the ball (ms-1)

t is time (s)

36
Q

Projectiles - Vertical Motion

A

The motion the ball would have if it had no horizontal velocity - if it were just dropped from a cliff

37
Q

Projectiles - Vertical Acceleration

A

9.8 ms-2

38
Q

Projectiles - Vertical Speed

A

Calculated using equation: vv=u+at

Where: vv is the vertical speed of the ball (ms-1)

u is the initial vertical speed of the ball (ms-1)

a is the acceleration (ms-2)

t is time (s)

39
Q

Projectiles - Initial Vertical Speed

A

Always 0 ms-1

40
Q

Projectiles - Vertical Displacement

A

Found using the area under the vertical velocity-time graph

41
Q

Satellite

A

Projectile circling the Earth at a constant altitude

42
Q

How Satellites Work

A

Fall towards the Earth at the same rate as the Earth’s surface is curving away from the satellite

43
Q

Satellites - Acceleration

A

A satellite travelling at a constant speed in a circular orbit is still being accelerated towards the Earth due to the force of gravity

44
Q

Satellites - Velocity

A

The direction the satellite is travelling is constantly changing so the velocity of the satellite is changing

45
Q

Satellites - Forces

A

The unbalanced force acting on the satellite causes a change in direction rather than speed

46
Q

Planet

A

Body which orbits around a central star

47
Q

Moon

A

Body which orbits around a planet

48
Q

Star

A

Large, naturally luminous gaseous body (such as the Sun) found in the centre of a solar system.

49
Q

The Sun

A

The star at the centre of our solar system

50
Q

Galaxy

A

System of billions of stars that is both spinning and moving. Our galaxy is called the Milky Way

51
Q

Andromeda

A

Nearest galaxy to Milky Way. It is 2.5 million light years away and is a large, spiral galaxy

52
Q

The Universe

A

The whole of space and contains millions of galaxies separated by empty space

53
Q

Light year

A

Unit of distance. (metres/m), distance light travels in one year. One light year = 9.4608x10^15 m

54
Q

Optical Telescope

A

A refracting telescope uses two convex lenses (mounted on either end of a light proof tube) to produce an image on the retina of an observer

55
Q

Objective lens

A

Produces an image at its focus partway down the tube using visible light. Larger diameter means more light can enter - so brighter image produced

56
Q

Eyepiece lens

A

Magnifies the image produced by the objective lens. For a large magnification the objective lens should have a long focal length and the eyepiece lens should have a short focal length

57
Q

Spectroscope

A

Used to split up light from a star into different wavelengths

58
Q

Continuous spectrum

A

The light emitted goes along the entire spectrum

59
Q

Line spectrum

A

Only emits certain frequencies of light

60
Q

Radio telescope

A

Large metal curved reflector (Large metal dish) that collects and directs the weak radio waves onto an aerial

61
Q

Gamma Ray Astronomy - Examples

A

The Fermi and Swift satellites use gamma Ray telescopes to investigate sources of cosmic rays to study supernova and black holes, such as the one thought to be at the centre of our galaxy

62
Q

X-Ray astronomy - Examples

A

Telescopes carried by satellites used for the study of black holes. Data received from outside our galaxy using x-ray telescopes indicate the presence of a massive cloud of very hot gas which provides important evidence supporting the big bang model

63
Q

Ultraviolet astronomy - Examples

A

Hot stars with a surface temperature greater than 10,000°C emit most of their energy as UV radiation. UV radiation detected from space has contributed to research into how stars are formed. Hubble satellite carries UV telescope

64
Q

Infrared Astronomy - Examples

A

Most of the universe may consist of dark matter consisting of gas and dust. Strong infrared sources are believed to be regions of space that are rich in gas and dust in which young stars are forming

65
Q

Satellite Period

A

The time it takes for one complete orbit of the Earth. This depends on the height of the satellite. Higher altitude means longer period

66
Q

Geostationary satellite

A
  • Orbit 36,000km above the surface of the Earth- Orbital Period = 24 hours- Therefore satellite appears to remain above the same point on the surface of the Earth- Used for worldwide communication and provide satellite TV signals
67
Q

Launch - Mass

A

To achieve lift the upwards thrust must be greater than the downward forces of weight and air resistance. To reduce weight, the rockets mass must be as small as possible

68
Q

Launch - Speed

A

To escape the gravitational pull of a planet or moon a rocket must achieve ‘escape velocity’. On Earth this is around 11.2 km/s

69
Q

During - Cosmic Radiation

A

Radiation and high energy UV, X-Ray and gamma rays will no longer be blocked by the Earth’s atmosphere. These are all damaging to humans

70
Q

During - Air Pressure

A

As we get higher in the atmosphere air pressure falls. As pressure drops the boiling point of blood and other fluids falls

71
Q

End - Debris

A

Satellites left in orbit can explode leaving lots of small fragments of debris in orbit. If even a tiny piece hits a satellite or manned mission it could completely destroy it

72
Q

End - Re-entry

A

A craft returning to Earth will typically be travelling at about 11 000 ms-1 which means it has a huge amount of kinetic and gravitational potential energy to lose

73
Q

Re-entry - Mass Shedding

A

Since kinetic energy is proportional to mass, making the mass of a space craft as small as possible means the kinetic energy the craft needs to lose is minimal

74
Q

Re-Entry - Friction

A

Good way to lose kinetic energy is maximising the amount turned into heat by friction. Unfortunately this significantly raises the temperature of the space craft

75
Q

Overcoming Heat

A

Covering in a thick heat shield which vaporises during re-entry (Eh=mlv)

Shuttle is positioned at a very careful angle so there is still enough kinetic energy converted into heat but astronauts are kept away from the heat

76
Q

Benefits - Our understanding of Earth

A

We can use satellites to look back at Earth using visible light and other EM waves to image and provide other information about the Earth

77
Q

Polar-Orbiting Satellites

A

In much lower orbit around the Earth than geostationary satellites. Orbit from pole to pole around every 100 minutes and provide much more detailed images of the Earth’s surface

78
Q

Benefits - Technology

A

Many of the technologies developed for space travel have applications in our everyfay lives. Eg.

Freeze-Drying

Solar Power

Memory Foam

National 5: Physics (3 decks)

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