A LevelPhysicsAQAExam QuestionsMeasurements & Their ErrorsUse of SI Units & Their Prefixes

Use of SI Units & Their Prefixes (AQA A Level Physics)

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Use of SI Units & Their Prefixes

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Use of SI Units & Their Prefixes

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11 mark

Which of the following does not specify a physical quantity?

  • A speed of 25 miles per hour

  • An object with a mass of five grams

  • A current of 1 milliamp

  • A material with a density of mass per cubic metre

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21 mark

Which of the following is not a SI base unit?

  • volt

  • kilogram

  • Kelvin

  • mole

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31 mark

Five values of capacitance are listed below.

5 pF

5 kF

5 fF

5 MF

5 nF

Starting with the smallest first, what is the order of increasing magnitude of these values of capacitance?

  • 5 kF → 5 fF → 5 MF → 5 nF → 5 pF

  • 5 pF → 5 fF → 5 nF → 5 kF → 5 MF

  • 5 fF → 5 pF → 5 nF → 5 kF → 5 MF

  • 5 fF → 5 kF → 5 nF → 5 MF → 5 pF

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41 mark

What is the SI base unit of gravitational field strength?

  • N

  • m s–2

  • N kg–1

  • J kg–1

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51 mark

The force, F, acting on a body is equal to the rate of change of momentum and can be calculated using the equation:

F equals fraction numerator m increment v over denominator increment t end fraction

Which of the following is a possible unit for the rate of change of momentum?

  • N s

  • N s–1

  • kg m s–1

  • kg m s–2

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61 mark

Impulse can be obtained from the area under a force-time graph, as shown in the diagram below.

 

q6

Which of the following is a possible unit for the area under a force-time graph?

  • N m

  • N s–1

  • kg m s–1 

  • kg m s–2

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71 mark

Some physical quantities can be measured directly, whereas others can only be estimated. Which of the following rows in the table is correct?

 

Physical quantity

Measurable or estimated

A

length of a football field

estimated

B

age of the universe

measurable

C

voltage of mains supply

estimated

D

reaction time of a person

measurable

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    81 mark

    Which product-pair of metric prefixes has the greatest magnitude?

    • pico × mega

    • nano × kilo

    • micro × giga

    • milli × tera

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    91 mark

    Which quantity can be measured in electronvolts (eV)?

    • electric charge

    • potential difference

    • energy

    • power

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    101 mark

    What is the ratio fraction numerator 10 to the power of negative 3 end exponent space T H z over denominator 10 cubed space k H z end fraction ?

    • 10–9

    • 10–6

    • 100

    • 103

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    11 mark

    The average kinetic energy E of a gas molecule is given by the equation

    E = 3 over 2 kT 

    where T is the absolute (Kelvin) temperature.

    What are the SI base units of k?

    • kg–1 m–1 s2 K

    • kg–1 m–2 s2 K

    • kg m s–2 K–1

    • kg m2 s–2 K–1

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    21 mark

    The units of all physical quantities can be expressed in terms of SI base units.

    Which pair contains quantities with the same base units?

    • force and momentum

    • pressure and Young’s modulus

    • power and kinetic energy

    • mass and weight

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    31 mark

    The table contains some quantities, together with their symbols and units.

    quantity

    symbol

    unit

    gravitational field strength

    density of liquid

    vertical height

    volume of part of liquid

    g

    ρ

    h

    V

    N kg–1

    kg m–3

    m

    m3

    Which expression has the units of energy?

    • rho g squared h

    • fraction numerator rho h V over denominator g end fraction

    • fraction numerator rho g over denominator h V end fraction

    • g rho h V

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    41 mark

    For which quantity is the magnitude a reasonable estimate?

    • frequency of a radio wave 500 pHz

    • mass of an atom 500 μg

    • the Young modulus of a metal 500 kPa

    • wavelength of green light 500 nm

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    51 mark

    2.5 kilowatt-hours (kW h) is equivalent to

    • 1.6 × 1022 eV

    • 1.6 × 1025 eV

    • 5.6 × 1025 eV

    • 5.6 × 1022 eV

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    61 mark

    Which of the following correctly expresses the Ohm in terms of SI base units?

    • kg m2 s–3 A–1

    • kg m2 s–3 A–2

    • J C–2 s

    • J C–2 s–1

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    71 mark

    Which one of the following cannot be used as a unit for electric field strength?

    • J m–1 C–1

    • J A–1 s–1 m–1

    • N A–1 s–1

    • J C m–1

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    81 mark

    The equation of hydrostatic pressure relates the pressure of a fluid, P, to the density of the fluid, ρ, and is given by

    P = ρgΔh

    Where g is the gravitational field strength, and Δh is the depth from the surface of the fluid.

    How can both sides of this equation be written in terms of base units?

    • (N m–1) = (kg m–3) (m s–1) (m)

    • (N m–2) = (kg m–2) (m s–2) (m)

    • (kg m–1 s–2) = (kg m–3) (m s–2) (m)

    • (kg m–1 s–1) = (kg m–1) (m s–2) (m)

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    91 mark

    The units of all physical quantities can be expressed in terms of SI base units.

    Which pair contains quantities with different base units?

    • emf and lost volts

    • stress and strain

    • impulse and momentum

    • pressure and Young’s modulus

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    101 mark

    Which of the following would be the most reasonable estimate for the energy of a photon of violet light?

    • 1 eV

    • 2 eV

    • 3 eV

    • 4 eV

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    11 mark

    Which formula could be correct for the speed v of ocean waves in terms of the density ρ of sea-water, the acceleration of free fall g, the height h of the wave and the wavelength λ?

    • v = square root of rho g h end root

    • v = square root of g over h end root

    • v = square root of g lambda end root

    • v = square root of g over rho end root

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    21 mark

    The drag coefficient Cd is a number with no units. It is used to compare the drag on different cars at different speeds. It is given by the equation

     Cd = fraction numerator 2 F over denominator rho v to the power of n A end fraction

     where F is the drag force on the car, ρ is the density of the air, A is the cross-sectional area of the car and v is the speed of the car.

     What is the value of n?

    • 1

    • 2

    • 3

    • 4

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    31 mark

    When a constant braking force is applied to a vehicle moving at speed v, the distance d moved by the vehicle as it comes to rest is given by the expression

    d = kv2

    where k is a constant.

    When d is measured in metres and v is measured in metres per second, the constant has a value of k1.

    What is the value of the constant when the distance is measured in metres, and the speed is measured in kilometres per hour?

    • 0.0772k1

    • 0.278k1

    • 3.60k1

    • 13.0k1

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    41 mark

    The frictional force F on a sphere falling through a fluid is given by the formula

    F = 6 pi a eta nu 

    where a is the radius of the sphere, η is a constant relating to the fluid and v is the velocity of the sphere.

    What are the units of η?

    • kg m s–1

    • kg m–1 s–1

    • kg m s–3

    • kg m–3 s–3

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    51 mark

    The speed v of a liquid leaving a tube depends on the change in pressure ΔP and the density ρ of the liquid. The speed is given by the equation

    v = k left parenthesis fraction numerator increment P over denominator rho end fraction right parenthesis to the power of n

    where k is a constant that has no units.

    What is the value of n?

    • 1 half

    • 1

    • 3 over 2

    • 2

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    61 mark

    Which estimate is realistic?

    • The kinetic energy of a bus travelling on an expressway is 30,000 J

    • The power of a domestic light is 300 W

    • The temperature of a hot oven is 300 K

    • The volume of air in a car tyre is 0.03 m3

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    71 mark

    The theory of gas flow through small diameter tubes at low pressures is an important consideration of high vacuum techniques.

    One equation used in this theory is

    Q = fraction numerator k r cubed left parenthesis p subscript 1 minus p subscript 2 right parenthesis over denominator L end fraction square root of fraction numerator M over denominator R T end fraction end root

    Where k is a unitless constant, r is the radius of the tube, p1 and p2 are the pressures at each end of the tube, L is the length of the tube, M is the molar mass of the gas, R is the molar gas constant and T is the thermodynamic temperature of the gas.

    What are the base units of Q?

    • kg s–1

    • kg m s–1

    • kg mol–1

    • kg m s–2

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    81 mark

    The conductivity of a metal is determined by how many free electrons it contains. The densities and relative atomic mass of four different metals is shown below.

    Metal

    Density / g cm−3

    Relative atomic mass

    Lead

    11.29

    207.2

    Copper

    8.96

    63.55

    Steel

    7.85

    55.85

    Aluminium

    2.71

    26.98

    Which row shows the correct order of the metals, from best thermal conductor to worst?

     You may take Avogadro's number to be 6.02 × 1023 mol−1 and you can assume each metal contributes one free electron per atom.

    • steel → copper → aluminium → lead

    • lead → aluminium → steel → copper

    • aluminium → steel → copper → lead

    • copper → steel → aluminium → lead

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    91 mark

    Each binary digit on a computer is called a bit. A series of eight bits forms a byte (B). A CD-ROM holds 650 megabytes (MB) of information.

    A typical book contains 200 pages or 240 000 characters.

    If each character is equal to 1 byte, how many books can be stored on the CD-ROM?

    • 3

    • 330

    • 2700

    • 170000

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    101 mark

    Which of the following is the best estimate for the mass of the Earth’s atmosphere?

    You may take Earth’s atmospheric pressure to be 1 × 105 Pa

    • 8 × 1011 kg

    • 6 × 1015 kg

    • 5 × 1018 kg

    • 2 × 1022 kg

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