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P1112
Fall 2008
Homework #11
Due: the week of Nov 1014
Reading: 9.19.4, 10.110.5
1.
A singlestage rocket with initial mass (rocket plus
fuel) m
0
is accelerated from rest from a deepspace
platform, where gravity is negligible. If the rocket
burns its fuel in a time of 50 s, and the relative speed
of the exhaust gas is 2100 m/s, so the mass is reduced
to m, what must the mass ratio m
0
/m be for a final
speed of 8.0 km/s ?
2.
A 20.0 kmprojectile is fired at an angle 60
o
above
the horizontal and with a speed of 80.0 m/s. At the
highest point of the trajectory the projectile explodes
into two fragments with equal mass, one of which
falls vertically with zero initial speed. Ignore air
resistance.
a)
How far from the point of firing does the other
fragment strike (level terrain) ?
b)
How much energy is released during the
explosion ?
3.
A flywheel with a radius of 0.3 m starts from rest
and accelerates with a constant angular acceleration
of 0.6 rad/s
2
. Compute the magnitude of the tangential
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 Fall '07
 LECLAIR,A
 Inertia, Mass, Work

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