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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Which of the following does not specify a physical quantity?
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Which of the following is not a SI base unit?
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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?Did this page help you?
What is the SI base unit of gravitational field strength?
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Which of the following is a possible unit for the rate of change of momentum?
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Impulse can be obtained from the area under a force-time graph, as shown in the diagram below.
Which of the following is a possible unit for the area under a force-time graph?
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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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Which product-pair of metric prefixes has the greatest magnitude?
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Which quantity can be measured in electronvolts (eV)?
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What is the ratio ?
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The average kinetic energy E of a gas molecule is given by the equation
E = 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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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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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?
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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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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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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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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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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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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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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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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 =
v =
v =
v =
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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
Cd =
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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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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The frictional force F on a sphere falling through a fluid is given by the formula
F =
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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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
where k is a constant that has no units.
What is the value of n?
1
2
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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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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 =
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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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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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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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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