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Lecture10 (Topic9) Dynamics of Rotational Motion, NG HUI YUN A20SC0187 -…
Lecture10 (Topic9)
Dynamics of Rotational Motion
Angular Momentum, L
objects rotating about a fixed axis
L=Iω
Στ=Iα=dL/dt
Conservation of Angular Momentum
The total L of a rotating object remains constant if the net external torque acting on it is zero.
Στ=0, dL/dt=0, L remains constant
Vector Cross Product
general form
C=ABsinθ
Vector Torque
torque = r × F
In diagram above, ω points upwards
τ due to F tends to increase ω
α will also point upwards (α=dω/dt)
L of a Particle
[particle, inertial frame]
L and τ
Στ=dL/dt is only for inertial reference frame
Exception:
[for CM even it is accelerating]
*for a rigid object
Rotational Imbalance
L and ω not in same direction
torque is needed to keep the unbalanced system rotating
NG HUI YUN
A20SC0187
