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Rocket Propulsion
Contents:Review
Types of Rockets
ExamplesWhiteboards
Microsoft Encarta
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So far we have:Impulse = Ft = mv
F = Force (N)
t = Elapsed time (s)m = Mass (kg)
v = Change in velocity (m/s)
Rocket Propulsion
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Rocket Propulsion
Ft
=
mv
So:F = engine thrust
t = time to burnfuelm = mass of fuel
burned
v= exhaust gasvelocity
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Which Rocket Accelerates faster?
A B
DemoF14
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Estes
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Lookout!
m = .5 kg, Ft = 20 Ns
Ft = m v
20 Ns = .5kg v
v = ? (x 2.237 for mph)
Estes
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Whiteboards
1| 2| 3
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Impulse = (10. N)(1.73 s-0.11 s) + (28 N-10 N)(0.42 - 0.21) = 19.98 Ns (about 20 Ns)
What is the impulse of the D12 engine?
W20 Ns
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A D12 engine generates 11.80 N of
thrust burning fuel at a rate of
.0143 kg/s. What is the exhaust
velocity?
825.2 m/s
Ft = mv
(11.80 N)(1 s) = (.0143 kg)v,
v = = 825.2 m/s
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A model rocket has a total mass of 235
grams, 145 grams of which is fuel. The
engine burns the fuel in 2.74 s, with anexhaust velocity of 890 m/s. What are the
initial and final rocket masses?
F = 47.1 N
.235 kg and .090 kg
Uh, initial = .235 kg
Final = .235 kg - .145 kg = .090 kg
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A model rocket has a total mass of 235
grams, 145 grams of which is fuel. The
engine burns the fuel in 2.74 s, with anexhaust velocity of 890 m/s. What is the
final rocket acceleration?
F = 47.1 Nmo= .235 kg, m = .090 kg, =ma(hint)
final = 514 m/s/s
=(.090 kg)(a), a=44.8 N/.090 kg=514 m/s2
W
