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A LevelPhysicsCIEExam Questions1. Physical Quantities & Units1.2 SI Units

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First teaching 2023

First exams 2025

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SI Units (CIE A Level Physics)

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1.2 SI Units

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1.2 SI Units

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1
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Which of the following is an SI base unit?

  • Current

  • Gram

  • Kelvin

  • Volt

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2
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Five energies are listed below.

5kJ

5mJ

5MJ

5nJ

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

  • 5 kJ space rightwards arrow 5 mJ space rightwards arrow 5 MJ space rightwards arrow 5 nJ

  • 5 nJ space rightwards arrow 5 kJ space rightwards arrow 5 MJ space rightwards arrow 5 mJ

  • 5 nJ space rightwards arrow 5 mJ space rightwards arrow 5 kJ space rightwards arrow 5 MJ

  • 5 mJ space rightwards arrow 5 nJ space rightwards arrow 5 kJ space rightwards arrow 5 MJ

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3
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Which product-pair of metric prefixes has the greatest magnitude?

  • pico × mega

  • nano × kilo

  • micro × giga

  • milli × tera

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4
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Which statement includes a correct unit?

  • Energy = 7.8 Ns

  • Force = 3.8 Ns

  • Momentum = 6.2 Ns

  • Torque = 4.7 Ns

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5
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Which quantity can be measured in electronvolts (eV)?

  • Electric charge

  • Electric potential

  • Energy

  • Power

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6
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Which of the following is not a SI base unit?

  • kilogram

  • metre

  • second

  • volt

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7
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Which product pair of metric prefixes has the smallest magnitude?

  • nano × mega

  • tera × pico

  • centi × kilo

  • micro × giga

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1
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The average kinetic energy E of a gas molecule is given by the equation

                  E equals 3 over 2 space k T

where T is the absolute (kelvin) temperature.

What are the SI base units of k?

  • kg to the power of negative 1 end exponent space straight m to the power of negative 1 end exponent space straight s squared space straight K space

  • kg to the power of negative 1 end exponent space straight m to the power of negative 2 end exponent space straight s squared space straight K space

  • kg space straight m space straight s to the power of negative 2 end exponent space straight K to the power of negative 1 end exponent

  • kg space straight m squared space straight s to the power of negative 2 end exponent space straight K to the power of negative 1 end exponent

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2
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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 modulus

  • Power and kinetic energy

  • Mass and weight

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3
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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 to the power of italic 2 h

  • fraction numerator rho h V over denominator g end fraction

  • fraction numerator straight rho g over denominator h V end fraction

  • g rho h V

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4
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What is the ratio fraction numerator 10 to the power of negative 3 end exponent space THz over denominator 10 cubed space kHz end fraction ?

  • 10-9

  • 10-6

  • 100

  • 103

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5
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Which of the following correctly expresses the volt in terms of SI base units?

  • AΩ 

  • WA–1

  • kg space straight m squared space straight s to the power of – 1 end exponent space straight A to the power of – 1 end exponent

  • kg space straight m squared space straight s to the power of – 3 end exponent space straight A to the power of – 1 end exponent space

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6
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The equation relating pressure and density is P space equals space rho g h

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

  • open square brackets straight N space straight m to the power of negative 1 end exponent close square brackets space equals space open square brackets kg space straight m to the power of negative 3 end exponent close square brackets open square brackets straight m space straight s to the power of negative 1 end exponent close square brackets open square brackets straight m close square brackets

  • open square brackets straight N space straight m to the power of negative 2 end exponent close square brackets space equals space open square brackets kg space straight m to the power of negative 2 end exponent close square brackets open square brackets straight m space straight s to the power of negative 2 end exponent close square brackets open square brackets straight m close square brackets

  • open square brackets kg space straight m to the power of negative 1 space end exponent straight s to the power of negative 2 end exponent close square brackets space equals space open square brackets kg space straight m to the power of negative 3 end exponent close square brackets open square brackets straight m space straight s to the power of negative 2 end exponent close square brackets open square brackets straight m close square brackets

  • open square brackets kg space straight m to the power of negative 1 end exponent space straight s to the power of negative 1 end exponent close square brackets space equals space open square brackets kg space straight m to the power of negative 1 end exponent close square brackets open square brackets straight m space straight s to the power of negative 2 end exponent close square brackets open square brackets straight m close square brackets

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7
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What is the product of 6 ×103 µs and 2 hrs and 3 × 10−3 Ms, expressed in seconds?

  • 36 s

  • 1.296 × 10−1 s

  • 1.296 × 105  s

  • 1.296 × 1011  s

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1
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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 equals k open parentheses fraction numerator increment P over denominator rho end fraction close parentheses 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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2
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The frictional force F on a sphere falling through a fluid is given by the formula

               F equals 6 straight pi straight a straight eta v

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 space straight m space straight s to the power of negative 1 end exponent

  • kg space straight m to the power of negative 1 end exponent straight s to the power of negative 1 end exponent

  • kg space straight m space straight s to the power of negative 3 end exponent

  • kg space straight m cubed space straight s to the power of negative 3 end exponent

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3
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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 equals k v squared

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 k when the distance is measured in metres, and the speed is measured in kilometres per hour?

  • 0.077 k subscript 1

  • 0.278 k subscript 1

  • 3.60 k subscript 1

  • 13.0 k subscript 1

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4
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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

                C subscript d space equals space 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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5
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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 equals square root of rho g h end root

  • v equals square root of g over h end root

  • v equals square root of g lambda end root

  • v equals square root of g over rho end root

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6
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The equation for the terminal velocity of a sphere of radius r falling under acceleration due to gravity, g, through a liquid with density ⍴ and viscosity ɳ, measured in kg m−1 s−1 is:

v subscript t equals 2 over 9 fraction numerator g r to the power of n rho over denominator eta end fraction

What is the value of n?

  • 0.5

  • 1

  • 2

  • 3

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7
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The current I through a semiconductor diode is given by:

I equals I subscript 0 e to the power of fraction numerator negative q V over denominator n T end fraction end exponent

Where I0 is the initial current, q is the charge of an electron, V is the applied potential difference, T is the temperature, and n is a constant. What are the units of n, expressed in base units?

  • n = C V K−1

  • n = kg m2 s−2 K−1

  • n = A s−1 V K−1

  • n = A kg m2 s−2 K−1

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