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AQA GCSE Physics (Detailed Version) > P8,9,10,11 > Flashcards

P8,9,10,11 Flashcards

1
Q

What is a scalar quantity?

A

● A quantity that only has a magnitude ● A quantity that isn’t direction
dependent

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2
Q

What is a vector quantity?

A

A quantity that has both a magnitude and an associated direction.

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3
Q

How can a vector quantity be drawn and what does it show?

A

● As an arrow
● The length of the arrow represents the magnitude
● The arrow points in the associated direction

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4
Q

What is a force?

A

A push or pull acting on an object due to an interaction with another object.

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5
Q

What are the two categories that all forces can be split into?

A
  1. Contact forces (objects touching)
  2. Non-contact forces (objects separated)
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6
Q

Give three examples of contact forces.

A
  1. Friction
  2. Air resistance
  3. Tension
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7
Q

Give three examples of non-contact forces.

A
  1. Gravitational forces
  2. Electrostatic forces
  3. Magnetic forces
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8
Q

Is force a vector or a scalar quantity?

A

● Vector
● It has both a magnitude and an
associated direction

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9
Q

Give three examples of vector quantities.

A
  1. Velocity
  2. Displacement
  3. Force
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10
Q

Give some examples of scalar quantities.

A

● Temperature
● Time
● Mass
● Speed
● Distance
● Energy

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11
Q

What is weight?

A

The force that acts on an object due to gravity and the object’s mass.

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12
Q

What quantities does weight depend on?

A

● The object’s mass
● The gravitational field strength at the given position in the field

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13
Q

What is the unit used for weight?

A

The Newton (N).

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14
Q

What is the unit used for gravitational field strength?

A

N/kg

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15
Q

What is meant by an object’s centre of mass?

A

The single point where an object’s weight can be considered to act through

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16
Q

What piece of equipment can be used to measure an object’s weight?

A

A calibrated spring-balance or newton- meter.

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17
Q

What is the name given to the single force that is equivalent to all the other forces acting on a given object?

A

The resultant force.

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18
Q

What does it mean if a force is said to do ‘work’?

A

The force causes an object to be displaced through a distance.

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19
Q

What distance must be used when calculating work done?

A

It must be the distance that is moved along the line of action of the force.

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20
Q

Under what circumstance is 1 joule of work done?

A

When a force of 1 Newton causes a displacement of 1 metre.

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21
Q

How many Newton-metres are equal to 1 joule of energy?

A

Nm = 1 J

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22
Q

How much work is done by the force of 10N acting on and object over a distance of 5m?

A

10 x 5 = 50 Nm
= 50 J

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23
Q

What occurs when work is done against frictional forces?

A

● A rise in temperature of the object occurs
● Kinetic energy is converted to heat

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24
Q

Why does air resistance slow down a projectile?

A

● The object does work against the air resistance
● Kinetic energy is converted in to heat, slowing down the object

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25
Q

Explain the relationship between the force applied and the extension of an elastic object.

A

The extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

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26
Q

What is meant by an inelastic (plastic) deformation?

A

● A deformation which results in the object being permanently stretched

● The object doesn’t return to its original shape when the force is removed

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27
Q

What type of energy is stored in a spring when it is stretched?

A

Elastic potential energy.

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28
Q

What can extension be replaced with in the equation for spring force?

A

Compression

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29
Q

What is an alternative name for the turning effect of a force?

A

A moment.

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30
Q

What distance measurement is used when calculating a moment?

A

The perpendicular distance from the pivot to the line of action of the force.

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31
Q

If an object is in equilibrium, what can be said about the moments acting on the object?

A

The clockwise moments are equal to the anticlockwise moments.

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32
Q

What three parts make up a lever system?

A
  1. Load
  2. Effort
  3. Pivot
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33
Q

How can a lever be used as a force multiplier?

A
  • Greater effort-to-pivot distance than pivot-to-load means greater force on the load.
  • Moment on effort = Moment on load
  • Applies principle of moments
34
Q

Give an example of when a lever may be used to multiply a force.

A

A wrench, which has a long handle so that the force applied by the user is multiplied.

35
Q

What determines the moment of a gear wheel?

A

The size of the wheel.

36
Q

Describe the moment and speed of a larger gear being driven by a smaller gear.

A

The larger wheel will rotate more slowly but will also produce a larger moment.

37
Q

What is meant by the term ‘fluid’?

A

A liquid or a gas.

38
Q

In any fluid, at what angle do the forces due to pressure act on a given surface?

A

At right angles (normal to) the surface.

39
Q

What happens to the density of the atmosphere with increasing altitude?

A

The atmosphere becomes less dense as altitude increases.

40
Q

Explain why atmospheric pressure decreases with an increase in height.

A

● Pressure is created by collisions of air molecules
● The quantity of molecules (and so weight) decreases as the height increases
● This means atmospheric pressure decreases with an increase of height

41
Q

What is the Earth’s atmosphere?

A

A thin (relative to the magnitude of the Earth) layer of gas surrounding the Earth.

42
Q

How does pressure in fluids increase with depth?

A
  • Depth increase → More liquid mass above.
  • More mass → Increased force due to gravity.
  • Force increases → Pressure increases (constant area).
43
Q

Why does pressure in fluids increase with density?

A
  • Higher fluid density → more particles in given volume → greater fluid weight.
  • Increased fluid weight → stronger force from fluid above.
  • Stronger force → higher pressure at that point.
44
Q

Why are objects in a fluid subject to an upthrust?

A
  • Submerged objects have higher pressure beneath than above due to fluid weight.
  • Result: Upwards force called upthrust acts on submerged objects.
  • Floating or sinking depends on upthrust compared to object’s weight.
45
Q

What is upthrust always equal to?

A

The weight of the fluid that the object displaces.

46
Q

What factors influence whether an object will sink or float?

A

● Upthrust
● Weight
● Density of fluid

47
Q

Explain why an object with a density greater than that of water can never float.

A
  • Upthrust = weight of displaced fluid.
  • High object density = less displaced volume.
  • Insufficient upthrust = object sinks.
48
Q

Does a distance quantity require a specific direction? i.e. Is it a scalar or vector quantity?

A

No specific direction is required so it is a scalar quantity.

49
Q

If an object moves 3 metres to the left and then 3 metres back to its initial position, what is the object’s total displacement?

A

● The object has zero displacement
● Displacement is a vector quantity so it also involves direction
● The object starts and ends at the same point

50
Q

State a typical value for the speed of sound.

A

330 m/s

51
Q

What is a typical value for human walking speed?

A

1.5 m/s

52
Q

What is a typical value for human running speed?

A

3 m/s

53
Q

What is a typical value for human cycling speed?

A

6 m/s

54
Q

Why can an object travelling at a constant speed in a circle not have a constant velocity?

A

● Speed is a scalar quantity

● Velocity is a vector quantity which means it can only be constant if the direction is constant

● In circular motion, the direction is continuously changing

55
Q

How can speed be calculated from a distance-time graph?

A

The speed is equal to the gradient of the graph.

56
Q

What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?

A

● Drawing a tangent to the curve at the required time

● Calculating the gradient of the tangent

57
Q

How can the distance travelled by an object be calculated from a velocity-time graph?

A

It is equal to the area under the graph.

58
Q

Give an approximate value for the acceleration of an object in free fall under gravity near the Earth’s surface.

A

9.8 m/s^2

59
Q

What can be said about the resultant force acting on an object when it is falling at terminal velocity?

A

● The resultant force is zero

● When at terminal velocity, the object is moving at a constant speed and so isn’t accelerating

60
Q

State Newton’s first law for a stationary object.

A

If the resultant force on a stationary object is zero, the object will remain at rest.

61
Q

State Newton’s first law for a moving object.

A

If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed in same direction).

62
Q

What can be said about the braking forces and driving forces when a car is travelling at constant velocity?

A

The braking forces are equal to the driving forces.

63
Q

If an object changes direction but remains at a constant speed, is there a resultant force?

A

Since there is a change in direction, there is a change in velocity and so there must be a resultant force.

64
Q

What is inertia?

A

The tendency of an object to continue in its state of rest or uniform motion.

65
Q

State Newton’s Second Law in words.

A

An object’s acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass.

66
Q

What is inertial mass?

A

● A measure of how difficult it is to change a given object’s velocity

● The ratio of force over acceleration

67
Q

What is the symbol used to represent an approximate value?

A

~

68
Q

State Newton’s Third Law.

A

Whenever two objects interact, the forces that they exert on each other are always equal and opposite.

69
Q

What is the stopping distance of a vehicle equal to?

A

The sum of thinking distance and braking distance.

70
Q

For a given braking distance, if the vehicle’s speed is increased, what can be said about its stopping distance?

A

The stopping distance is increased with an increase in speed.

71
Q

Give a typical range of values for human reaction time.

A

0.2 seconds - 0.9 seconds

72
Q

Give three factors which can affect a driver’s reaction time.

A
  1. Tiredness
  2. Drugs
  3. Alcohol
73
Q

Give two factors which may affect braking distance.

A
  1. Adverse (wet/icy) road conditions
  2. Poor tyre/brake conditions
74
Q

Describe the energy transfers that take place when a car applies its brakes.

A

● Work is done by the friction force between the brakes and wheel

● Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings through the brake discs

75
Q

To stop a car in a given distance, if its velocity is increased, what must happen to the braking force applied?

A

The braking force must also be increased.

76
Q

State two consequences of a vehicle undergoing very large decelerations.

A
  1. Kinetic energy converted to heat is very high causing brakes to overheat
  2. Loss of control of the vehicle
77
Q

What is the unit used for momentum?

A

kg m/s

kilogram metres per seconds

78
Q

In a closed system, what can be said about the momentum before and after a collision?

A

The total momentum before is equal to the total momentum afterwards.

79
Q

What quantity is equal to the force experienced in a collision?

A

The rate of change of momentum.

80
Q

If an object’s change of momentum is fixed, what is the only way to reduce the force that the object experiences?

A

Increase the length of time over which the change of momentum occurs.

81
Q

Explain how a seatbelt improves a passenger’s safety during a collision.

A

● Passenger must decelerate from the vehicle’s velocity at impact to zero, meaning they undergo a fixed change of momentum

● The force they experience is equal to the rate of change of momentum

● Seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and therefore reducing the force experienced

AQA GCSE Physics (Detailed Version) (27 decks)

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