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Student Responses to Rocket Questions:

10/6/96,1835 sName,CM
sSection,110z M3
honor,on
Q1,M= total mass
delta m = fuel change
v= velocity of rocket
delta t = the short time that the rocket fires
vex = the velocity if the exhaust
This wouldn' tbe hard to figure out for a model rocket but for a huge intercontinental, you would have to keep track of it when it reentered the atmosphere, too.
Q2,I am not sure what to do without the original velocity and because of that what the change in velocity is. I am looking over page 243.
Q3,a
1D,SUBMIT HOMEWORK

10/6/96,2132 sName,MH
sSection,M1
honor,on
Q1,You would have to know the time of burning, the exhaust velocity, and the thrust. This would be a very hard calculation for a model rocket due to its small mass, small exhaust velocity, and and the thrust velocity would be hard to calculate. A huge intercontinental missile would be much easier due to its extreme amounts of mass, thrust, and velocity.
Q2,M dV/dT= -Vex dM/dT
2,000,000 16m/s = -4000m/s (x/1s)

8000kg or 17,636lbs
Q3,a
1D,SUBMIT HOMEWORK

10/7/96,1229 sName,TA
sSection,M1
honor,on
Q1,There would be a change in the velocity due to the smaller gravitational pull. In a vacuum it would be even greater. It would work since the thrust pushes against the shuttle and not the air.
Q2,The red ball is heavier since it kept closer to its original trajectory.
Q3,d
1D,SUBMIT HOMEWORK

10/7/96,1238 sName,TA
sSection,M1
honor,on
Q1,You would need to know the rate of fuel consumption, and the change in velocity with time. The change in mass in velocity would be different numbers, but not larger calculations.
Q2,about 4,000 kg of fuel is burnt

4000m/s = 2e6 kg * 8 M/s%5E2
Q3,a
1D,SUBMIT HOMEWORK

10/7/96,1426 sName,MF
sSection,M3A
honor,on
Q1,You would need to know either the change in mass, exhaust velocity, and thrust, or the mass of the rocket, change in velocity, and thrust. An example is a model rocket with Thrust of 100 N, a mass of .5 kg, and a change in velocity of 40 m/s, burns fuel in .2 s.
Q2,Using the equation (dm/dt)*Ve= m*dv/dt, to find the change in mass we change the equatin so that it is dm=mdv/Ve. We then find dm to be 4000 kg.
Q3,a
1D,SUBMIT HOMEWORK

10/7/96,1611 sName,TB
sSection,M3A
honor,on
Q1,You would of course need to know masses,
and velocities. Also size may be of
importance because of drag. A large
rocket is affected more by drag then
a smaller rocket but the small one
may be affected more by wind then the
large one.

Q2,ma = Fext - Ve(dm/dt)

4000kg of fuel in the first second.

Q3,a
1D,SUBMIT HOMEWORK

10/7/96,2310 sName,RH/DM
sSection,M3A
Q1,We need to know the mass and the
final velocity. The model rocket would
not be a simple calculation it would be
the same as the huge missile and shuttle.
Q2,It burns 2000 kg of fuel per second.
Q3,a
1D,SUBMIT HOMEWORK

10/7/96,2341 sName,JD
sSection,M3A
Q1,need to know thrust change in exhaust velocity or mass and change in velocity.
Q2,dv/dt=a
dm/dt*ve=ma
dm=(2millkg*8*1)%5C4000m/s
4000kg
Q3,a
1D,SUBMIT HOMEWORK

10/7/96,2352 sName,DB
sSection,M1A
honor,on
Q1,We wouldn't hear it take off. The shuttle would accelerate faster because the acceleratoin due to gravity would be less on the moon, and in a vacuum it would not experience air resistance. The launch would still work in a vacuum because teh propulsioin of a rocket stems from the expansion of molecules pushing against teh nozzel, rather than molecules pushing against other particles.
Q2,The red ball has a greater mass because it's trajectory is chnged less after impact, whereas teh blue ball is projected at a sharp angle to the initial propulsion of the red ball.
Q3,b
1D,SUBMIT HOMEWORK

10/8/96,0022 sName,BL
sSection,M3A
honor,on
Q1,you would have to know how quickly the rocket
burns its fuel and how much fuel it carries.
This would definitely be an easier calculation
for the model rocket.
Q2,It uses approximately 4000 kg of fuel.
Q3,c
1D,SUBMIT HOMEWORK

10/8/96,0057 sName,JM
sSection,M3
honor,on
Q1,You would have to know the time interval, the final and initial velocities over that interval and the change in mass of the rocket. An intercontinental missle would be the same data, but the mass would be much greater.
Q2,I tried using the formula in the book from page 244, ex 10-9, but ended up with it only using 8.88 kg of fuel in 1 sec, which i know is way too little for that powerful of a rocket. I think i may have the wrong formula.
Q3,a
1D,SUBMIT HOMEWORK

10/8/96,0908 sName,?M
sSection,M1
honor,on
Q1,I would have to know the mass of the rocket and the acceleration of the rocket; I THINK that both calculations would be about as 'simple'
Q2,4000--seems too large
Q3,a
1D,SUBMIT HOMEWORK

10/8/96,0908 sName,LB
sSection,m1
honor,on
Q1,you would need to know Ve,the force exerted, and the time of burn
Q2,8900kg of fuel
Q3,c
1D,SUBMIT HOMEWORK

10/8/96,0914 sName,MK
sSection,m1a
honor,on
Q1,You would have to know the rockets thrust, velocity and weight. The calculation would be the same for both of the rockets, just different values.
Q2,It would burn 1000kg a second.
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,1438 sName,BH
sSection,
Q1,You would have to know the mass, exhaust velocity, and the acceleration. You would also need to know what time interval you want to use. They would both be hard calculations if you were supposed to figure out the exhaust velocity of each type of rocket.
Q2,About 4000 kg per second.
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,1648 sName,RG
sSection,M1A
honor,on
Q1,Exhaust velocity and mass. Yes it would be a simple calculation ignoring drag. With a huge intercontinetal missle you can ignore drag intialy (Much like the shuttle).
Q2,
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,1854 sName,CL
sSection,M1A
honor,on
Q1,You would have to know the original mass, the exhaust velocity and the acceleration. The acceleration of a huge missile would be slower than that of a small model rocket, making the model rocket's acceleration calculation much more difficult.

Q2,using the conservation of momentum equation, the rocket burns about 400 kg per second.
Q3,c
1D,SUBMIT HOMEWORK

10/9/96,2037 sName,?C
sSection,
honor,on
Q1,MASSi and MASSf
Ve
Vi Vf
yes
even easier, as it is with the space shuttle
Q2,About 1/10 of its supply, a little less
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,2050 sName,?M
sSection,T1
honor,on
Q1,You need to know the exhaust velocity, mass (including feul), the acceleration, and the time incriment. then solve for dm (change in mass, which is the mass of the fuel that burned.) It would be easier to calculate for a large missle because the fuel doens't burn off as quickly, comparitvley speaking.
Q2,ma = (dm/dt) Ve
(2.0x10%5E6)(8) = (dm/1) (4000)
dm = 4000 kg
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,2134 sName,OE
sSection,
honor,on
Q1,You would need to know the mass of the rocket at each interval of time you wanted to calculate because for a model rocket the mass changes very rapidly. Therefore the calculation would be relatively difficult. For a large intercontinental missle the change in mass would not be a dramatic therefor the calculation would be considerably simpler.

Q2,I need help with this one. I'm sure it's obvious, but I can't see it right now.
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,2251 sName,ND
sSection,M-3/4 A
honor,on
Q1,The velocity of the exhaust, the mass of the
rocket, the change of time, and the acceleration
of the rocket. It would be hard because
the acceleration of the rocket is hard
to calculate. THe intercontinental rocket
would be much easier.
Q2,dm/dt ve=m dv/dt
dm/1 4000=(2000000)8
dm =4000
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,2306 sName,JK
sSection,M1A
honor,on
Q1,you would have to know the exhaust velocity, the mass of the rocket and
the speed of the rocket

it would be a simple calculation for a model rocket and for a huge intercontinental missile
Q2,shuttles velocity = 8 m/s
exhaust velocity = 4000 m/s
shuttles mass = 2.0 x 10%5E6 kg

8 m/s divided by 4000 m/s = .002 m/s
ln(Mi/Mf) = .002
2.0 x 10%5E6 / Mf = e%5E.002
Mf = 1.996 x 10%5E6 kg in fuel burned during the first second
Q3,a
1D,SUBMIT HOMEWORK

10/9/96,2342 sName,CM
sSection,M 1/2 A
honor,on
Q1,You would have to know the change in mass (easy), the velocity (harder), and the velocity of exhaust from the rocket (hard). To find the amount of fuel burned it would be easiest to weigh the rocket before and after the launch, to get the mass of fuel lost. You could do the same for the missile.
Q2,about 39,240 kg.

maam, doesn't this next problem depend on whether or not the boosters are still providing thrust when they seperate, and how much???
Q3,d
1D,SUBMIT HOMEWORK

10/10/96,0023 sName,SC
sSection,M3
honor,on
Q1,You would need to know the rockets initial mass and the exhaust velocity. No, it would probably be hard to determine the exhaust velocity. The exhaust velocity should already be known for the missle which would make the calculations easier.
Q2,3995.58 kg
Q3,c
1D,SUBMIT HOMEWORK

10/10/96,0035 sName,RH
sSection,M1A
honor,on
Q1,You would have to know the change of the speed of the rocket, the velosity of the exaust, mass of the rocket. For a model rocket, it would accelerate at 4m/s%5E2, with the exaust moving at 2m/s, and have a mass of 1.5 kg. That will give a chang in mass of 1 kg/s. For a big missle, it will accelerate at 4 m/s%5E2, with exaust moving at 500 m/s, and have a weight of 700,000kg. This would make it loose 5600 kg/s.
Q2,4000
Q3,b
1D,SUBMIT HOMEWORK

10/10/96,0048 sName,CA
sSection,m3a
honor,on
Q1,to find the change in time you would need to know the change in mass, the exhaust velocity, and the time. this would be relatively easy to find using a model rock because you can see all of its motions. for the same reason it would be much harder to make this calculation for an icbm.
Q2,50,000 kg
Q3,b
1D,SUBMIT HOMEWORK

10/10/96,0057 sName,JB
sSection,M1/2
honor,on
Q1,I would have to know the mass of the rocket and the time . For the model rocket this would be a simple calculation because it is relatively small and does not have that great a mass change, also its flight is not very long. For the ICBM would this equation would be difficult to use becaue there is such a large change.
Q2,I know I would have to solve for change in mass, but I'm not really sure how to.
Q3,d
1D,SUBMIT HOMEWORK

10/10/96,0104 sName,DB
sSection,M1A
honor,on
Q1,We would have to know the rocket's exhaust velocity and starting mass, and be able to calculate the changes in velocity and mass with respect to time. This would not be easy to calculate for our model because the mass changes so rapidly we'd have to be extremely precise. The ICBM would be more forgiving (get a fairly close answer to the actual) if our changes in mass and velocity over a certain time were a little off (not precise).
Q2,4000 kg

I found this by plugging into the equation M Dv/Dt = -Vex DM/Dt
Q3,a
1D,SUBMIT HOMEWORK

10/10/96,0111 sName,BF
sSection,M3A
Q1,You would have to know the initial mass of the total rocket, as well as the mass of the fuel. The calculations would be the same for the model and the missle.
Q2,500kg
Q3,b
1D,SUBMIT HOMEWORK

10/10/96,0150 sName,RK
sSection,M3A
honor,on
Q1,You would need to know the velocity, the time of flight, the initial mass and the final mass. You would need to know how much fuel the rocket can hold. This calculation if fairly simple for a model rocket, and a huge intercontinental missle should follow the same basic guidelines, however there will be more complex external and internal factors involving it.
Q2,Using the equation M*(delta v/delta t)= -vex * (delta M/delta t), you can find the change in mass. Approximately 4000 kg of fuel are burned in the first second.
Q3,a
1D,SUBMIT HOMEWORK