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1
CENTRE OF MASS
& ROCKET
PROPULSIONMECHANICS & PROPERTIES OF MATTER
GROUP VII
2
CONTENTCentre of Mass What is Centre of Mass? Centre of Mass of symmetrical shape The Centre of Mass point for two mass system
• 2D• 3D
Rocket Propulsion
3
CENTRE OF MASS-(CM)• The location where all the mass of system could
be concentrated to be located.•Make responses to the external forces and
torques.• Distribution of mass is balanced around the CM.•Weighted average position coordinates defines
the position.
M1 M2CM
4
CENTRE OF MASS OF
SYMMETRICAL SHAPES
5
CM OF TWO IDENTICAL MASSES
l lm m
CM
6
UNIFORM ROD
ll
CM
7
SOLID TRIANGLE PLATE
x
x x
CM
8
CIRCLE
r
r
rr
CM
9
CUBOID
CM
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THE CENTRE OF MASS POINT FOR
TWO-MASS SYSTEM
11
CMm1 m2
x
x1x2
Reference axis𝑥=
𝑚1 𝑥1+𝑚2𝑥 2𝑚1+𝑚2
12
If the system is consist of “n” no. of mass particles,the position of the CM will be,
13
In the case of a 3D system,Y
Z
X
r1
rn
R(n-1)
R(n-2)r5
r4
r2
r3
m1
m5
m(n-1)
m4
m3
m2
mn
m(n-2)
CM
Position vector of CM is =x+y+z
{xi+yi+zi}
Where the position vector of mass of the system
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ROCKET PROPULSION
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• Based on the concept of “CONSERVATION OF MOMENTUM”
V
M
at time “t”
M
V+
Ve
Δ𝑚
at time “t+t”
16
THANK YOU !!!