PHY 222 Lecture Notes - Lecture 3: Laminar Flow, Dynamic Equilibrium, Viscosity
Dynamic equilibrium
A body in motion continues its motion with constant velocity
Derive the second law using momentum
F=dP/dt
P=mv
if m is constant
F=m(dv/dt)=ma
Newton's Third Law
When two bodies interact, the forces on the bodies from each other are equal in magnitude and
opposite in direction.
Forces on a flat plane
N=mg
Forces on an inclined plane
N=gosθ
Centre of mass
xcm=(m1x1+m2x2)/(m1+m2)
= (m1x1+m2x2)/M
Uniform mass distribution
r=/M∫rd
Centre of mass of a ruler
dm/M=dx/L
dm=M/L dx
=/M∫d ith liits L to
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= /M∫M/L d
=/L∫d
xcm=1/L[x²/2] =L/2
Static friction
F=ma
Fext-ƒs=
Fet=ƒs
ƒsa=µsN
Kinetic friction
ƒk=µkN
Laminar flow
Stoke's Law: Drag force of sphere in laminar flow
Dl=6ηr D proprtioal to
η=isosit
Turbulent Flow
Dt=0.5CpAv²
Cp= drag coefficient
A= cross sectional area
Work done
W=Fd
Hooke's Law
Fs=-kx
W=-1/2kx²
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