Flashcards in Unit 1 - Our Dynamic Universe Deck (103):

1

##
What is a scaler quantity?

### Quantity with size only.

2

##
Give some examples of scalor quantities.

### Distance, speed, time, mass, energy, power, temperature.

3

##
What is a vector quantity?

###
Quantities with magnitude and direction.

4

##
Give some examples of vector quantities.

### Displacement, velocity, acceleration, force, weight, momentum.

5

## How is magnitude and direction found from a vector diagram?

###
Magnitude -Pythagoras

Direction -trigonometry (SOH-CAH-TOA)

6

## How is velocity of a horizontal vector found?

### VcosO

7

## How is force of a vertical vector found?

###
FsinO

8

## What angle is always used when finding rectangular components of vectors?

###
Angle to the horizontal.

9

## When displacement is constant, what do the velocity and acceleration graphs look like?

### Both are a straight line at 0 along the x-axis.

10

## When velocity is constant what happens to the displacement on a motion-time graph?

###
Increases.

11

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When there is a constant positive acceleration, what does the displacement - time graph look like?

###
Smooth increasing curve ( _/ ) ➡️↗️.

12

## When there is a constant positive acceleration what happens to velocity?

### Velocity increases from zero upwards.

13

##
When there is a constant negative acceleration what happens to the displacement?

###
Smooth upwards curve ↗️➡️.

14

## How could displacement be found from a velocity-time graph?

###
Area under graph.

15

##
How could acceleration be found from a velocity-time graph?

###
Gradient of line.

16

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How would velocity be found from a velocity time graph?

### Value from best fit line.

17

## How would displacement be found from a displacement-time graph?

### Value from best fit line.

18

## How would velocity be calculated from a displacement-time graph?

###
Gradient of line.

19

## How would acceleration be found from a displacement-time graph?

### Calculate from velocity values, a = v-u/t.

20

## What indicates a change in direction on a velocity-time graph?

### Crossing the x-axis.

21

## Define acceleration.

### Change in velocity per second.

22

## From the equation a + v-u/t what does the u and v represent?

###
u = starting velocity.

v = final velocity.

23

## What experiment can be used to find the acceleration of an object?

### Measured using a trolley with a mask(s) and light gate(s).

24

## What measurements would need to be made when measuring acceleration?

###
- length of mask

- time through light gate(s)

- time between light gates or time between masks

25

## What is Newton's first law of motion?

### An object will remain at rest or continue in at a constant speed unless acted on by an unbalanced force.

26

##
What is Newton's second law?

### An unbalanced force will cause an object to accelerate.

27

## In what direction does friction act relative to the object?

###
In the opposite direction.

28

## How can the unbalanced force be calculated?

### F = Fh - Ffric.

29

## What is tension?

### The pulling force acting on a cable.

30

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When a lift is stationary or moving at a constant speed are the forces balanced or unbalanced?

###
Balanced.

31

##
When are the forces unbalanced in a lift?

### When the lift is accelerating or decelerating.

32

## When is the value for 'a' negative?

###
Accelerating down or decelerating up.

33

## In the rocket example of vertical thrust when are the forces balanced?

### When rocket is stationary.

34

## When is the value for 'a' in the equation T = mg + ma positive?

### Accelerating up or decelerating down.

35

## Why does a rocket acceleration increase?

###
Mass decreases - fuel used up.

Weight decreases -acceleration due to gravity decreases.

Air less dense - air resistance decreases.

36

##
How is Wpara calculated?

###
Wpara = mgsin(angle)

37

## How is Wperp calculated?

### Wperp = mgcos(angle).

38

##
How is the force calculated if the object is moving up a slope?

### F = Wpara - Ffric

39

## When is the equation F = Wpara + Ffric used?

### When an object is moving up the slope.

40

## Define work done?

### Amount of energy transferred from one place to another.

41

## What is power?

### The amount of energy transferred per second.

42

## If no friction acts on a slope how does the energy at the top and bottom compare?

### Ep at top = Ek at bottom

43

## If friction acts on a slope how does the energy at the top and bottom compare?

### Ep at top > Ek at bottom

44

## As friction acts on a slope how would the potential energy be found?

###
Ep = Ek at bottom + friction (Ew)

45

##
What is momentum?

### The product of an objects mass and velocity.

46

## What is the conservation of linear momentum?

### The total momentum before an interaction is equal to the total momentum after an interaction, in the absence of net external forces.

47

##
How is total momentum found?

### m1u1 = m2u2

48

## How is momentum calculated in a nonstick collision?

###
m1u1 + m2u2 = m1v1 + m2v2

49

## How is momentum calculated in a sticking collision?

### m1u1 + m2u2 = (ml + m2) v

50

## How is momentum calculated in an explosion?

###
(ml + m2) u = m1v1 + m2v2

51

##
In what type of collision is energy conserved?

### Elastic collision.

52

## What does the term 'energy conserved' mean?

### Ek total before = Ek total after

53

##
In what type of reaction is energy not conserved?

###
Inelastic collision.

54

##
How is kinetic energy calculated?

### Ek = 0.5 m1u1^2 + 0.5 m2u2^2

55

## What is impulse?

### The change in momentum.

56

##
What is impulse measured in?

### Ns

57

##
What needs to be taken into account when calculating impulse?

### Direction of the velocities and force.

58

##
On an impulse graph, how does a hard surface compare to a soft surface ?

###
Hard surface - high force, short time

Soft surface - small force, long time.

59

## How can impulse (Ft) be calculated from a graph?

### Ft = 1/2 bh (Area under graph)

60

## What is needed to measure contact time?

### A fast timer.

61

## What is a projectile?

### Objects moving under their own interia and so only affected by the force of gravity.

62

## What is interia?

###
An objects resistance to change.

63

## What are the requirements for a projectile?

###
- Constant horizontal velocity

- Constant vertical acceleration

64

## For a full projection how is the horizontal velocity calculated?

### Uh = vcos(angle)

65

## For a full projection how is the vertical velocity calculated?

### Uv = vsin(angle)

66

## What is gravitational attraction between two objects directly proportional to?

###
The mass of each object.

67

## What is gravitational attraction inversely proportional to?

### The square of the objects separation.

68

## What decreases as you move away from a planet's surface?

### Gravitational field strength of a planet.

69

## Why do occupants of a space shuttle appear weightless?

### Occupants are accelerating towards the earth at the same rate as the space shuttle making them appear weightless.

70

## What are the two postulates for special relativity?

###
- Laws of physics are the same for all observers.

- Speed of light the same for all observers.

71

## In the time dilation equation what does 't' represent?

### Time interval for moving observer.

72

## In the time dilation equation what does 't^l' represent?

### Time interval for a stationary observer.

73

## Is time interval for a stationary observer longer or shorter than that experienced by a moving observer?

### Time interval longer for stationary observer.

74

## What is length contraction?

### The muons are considered to be moving a different distance in the same amount of time.

75

##
For length contraction, what observer experiences the shortest distance?

### Stationary observer.

76

## What does the Doppler effect show?

### Shows how the detected frequency from a source can change depending on the relative motion between the source and the observer.

77

## What happens to the frequency of the waves as the source approaches?

### Frequency increases, more waves detected per second.

78

##
As the source moves away what happen to the frequency of the source ?

### Frequency decreases, less waves detected per second.

79

## Using the Doppler effect equation, what sign is used when the source is moving towards an observer?

### Negative (-).

80

## Using the Doppler effect equation, what sign is used when the source is moving away from an observer?

### Positive (+).

81

## What is Doppler redshift?

### Occurs when the light from an object that is moving away from us is ‘shifted’ towards the longer wavelength end.

82

## What does a larger redshift tell us about a galaxy?

### Galaxy is moving away from us at a faster rate.

83

## What happens to the wavelengths of light if an object that is moving towards us?

### Blueshifted.

84

## Where did the galaxy come from?

### A large cloud of dust and gas called nebula.

85

## What attracted the smaller particles together?

### Electromagnetism.

86

## What were the larger clumps attracted by?

### Force of gravity.

87

## What evidence is there for the expanding universe theory?

###
- Darkness of night sky.

- Redshift of most galaxies.

- Abundance of light elements.

- Cosmic Microwave Background Radiation (CMBR)

88

## What colour are hotter stars?

### Blue

89

## Are more distant galaxies moving away from us at a faster or slower rate than nearby galaxies?

### Faster

90

## What is dark matter?

###
From of matter that doesn't emit radiation in the electromagnetic spectrum.

91

## What does dark matter help to explain?

### Galaxies are revolving at a faster rate than predictions suggest.

92

## What is the calculated amount of dark matter not enough to stop?

### The expansion of the universe.

93

## What is dark energy?

### The unknown force that acts against the force of gravity.

94

## What does dark energy cause?

### Causes the expansion of the universe to accelerate.

95

## Is the rate of expansion of universe increasing or decreasing?

### Increasing.

96

## What are distant galaxies driven apart by?

### Dark energy.

97

## What is the colour of a star related to?

### It's temperature.

98

## What colour are cooler stars?

### Red.

99

## What are the properties of hotter stars relating to the radiation spectrum?

###
- Short wavelength

- High frequency

- High peak

- Large area of graph

100

## What are the properties of cooler stars relating to the radiation spectrum?

###
- Long wavelength

- Low frequency

- Low peak

- Small area of graph

101

## What is the peak wavelength of a star is inversely proportional to?

### It's surface temperature.

102

## What is the surface temperature of a star directly proportional to?

### Peak frequency of a star.

103