HW.cH5 em 5 tem 5 A 2420-kg test rocket is launched vertically from the launch p
ID: 1554494 • Letter: H
Question
HW.cH5 em 5 tem 5 A 2420-kg test rocket is launched vertically from the launch pad. Its fuel (of negligible mass) provides a thrust force so that its vertical velocity as a function of time is constants and time is measured from the instant the fuel is ignited. At the instant of ignition, the rocket has an upward acceleration of 1.10 m/s2 and 1.80 s later an upward velocity of 2.02 m/s Part A Determine A. Submit My Answers Give Up Part B Determine B. Submit My Answers Give Up Part C At 3.80 s after fuel ignition, what is the acceleration of the rocket?Explanation / Answer
A)
V = At + Bt²
dV/dt = a = A + 2Bt
when t = 0, a = 1.10 m/s²
A = 1.10 m/s2
when t = 1.80 s, V = 2.02 m/s
B)
2.02 = 1.10(1.80) + B(1.80)² = 1.98 + 3.24B
B = 0.04/3.24 = 0.0123
C)
a = 1.10 + 0.0123t
at t = 3.80 s, acceleration, a = 1.10 + 0.0123(3.80) = 1.147m/s2
D)
The Rocket's Thrust = ma = 2420(1.10 + 0.0123(3.80)) =2692 N
E)
Rocket's weight = 2420(9.81) = 23716 N
Thrust = 2692/23716 = 0.114 = 11.4% of rocket's weight at t = 3.80 s
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