In: Physics
The VASIMR Rocket NASA plans to use a new type of rocket, a Variable Specific Impulse Magnetoplasma Rocket (VASIMR ), on future missions. If a VASIMR can produce 6.0 N of thrust (force), and has a mass of 620 kg, (a) what acceleration will it experience? Assume that the only force acting on the rocket is its own thrust, and that the mass of the rocket is constant. (b) Over what distance must the rocket accelerate from rest to achieve a speed of 9500 m/s?. (c) When the rocket has covered one-quarter the acceleration distance found in part (b), is its average speed 1/2, 1/3 or 1/4 its average speed during the final three-quarters of the acceleration distance? Explain.
(a) Newton second Law of motion
F = m a
acceleration
a = F / m
= (6 N) / 620 kg
= 0.0097 m /s2
(b)
Applying equation of motion,
v2 = vo2 +2 a Δx
Δx = (v2 -vo2 )/ 2 a
= ((9500 m /s)2 - 0) / 2 a
= 9500*620/(2*6)m
= 490833.33 m
(c)
if we take s as the acceleration distance then we get
d = (1 / 2) a T2
where T is the total time
T = √(2 d / a)
now the time to travel one half of the distance is given by
t = √[2(1 / 2)d / a]
= √(d / a)
= (1 / √2) T
= 0.7078 T
so for the first half of the distance the averagespeed is (1 / 2) d / 0.707 T
for the second half
(1 / 2) d / T - 0.707 T = (1 / 2) d / 0.293T
solve for the ratio
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