Learner Resource 1
Definitions of terms used in circular motion
Term
Definition
Unit
Period, T
Angle at centre of circle
subtended by an arc equal
to the radius
second, s
Frequency, f
Rate of change of angular
displacement
Hertz, Hz
Angular velocity, ω
Number of complete cycles
per second
radians per second, rad s-1
Angle
Time taken for one
complete cycle
radian, rad
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Circular and Simple Harmonic Motion
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Equations
Term
Centripetal acceleration, a
Centripetal acceleration, a
Definition
𝑎=
𝐹=
Unit
𝑣2
𝑟
ms-1
𝑚𝑣 2
𝑟
rad s-1
Centripetal force, F
v=ωr
m s-2
Constant speed in a circle,
v
𝑎 = 𝜔2 𝑟
Newtons
Centripetal force, F
ω = 2π / T, or ω = 2πf
m s-1
Angular velocity, ω
𝐹 = 𝑚𝜔2 𝑟
Newtons
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Circular and Simple Harmonic Motion
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Definitions of terms used in oscillations
Term
Period, T
Frequency, f
Displacement, x
Definition
maximum magnitude of
displacement from
equilibrium point
the number of complete
cycles in one second
part of a cycle by which two
oscillations of the same
frequency are out of step
Unit
Hertz, Hz
rad s-1
metres, m
Phase difference
overall change in position
from equilibrium point
ms-2
Acceleration in SHM, a
the time taken for one
complete cycle
ms-1
Amplitude, A
𝑣 = ±𝜔 √𝐴2 − 𝑥 2
ms-1
Velocity, v
vmax = ωA
seconds, s
Maximum velocity, vmax
angular displacement in unit
time
metres, m
Angular frequency, ω
a = -ω2x (definition of SHM)
radians
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