Magnitude of thrust of rocket (q50)

Thread starter jack1234
Start date Nov 7, 2007
Tags

Magnitude Rocket Thrust

AI Thread Summary

The discussion centers on the calculation of thrust for a rocket problem, specifically using the formula ma=(3000-800)*20 to arrive at a thrust of 44kN. The user questions whether this approach is correct, noting they did not utilize the thrust equations involving exhaust velocity and mass flow rate. Responses indicate that the problem may not fundamentally require a deep understanding of rocket dynamics. The consensus suggests that while the user's method yields a correct answer, it overlooks more comprehensive rocket thrust principles. Clarity on the appropriate approach to such problems is emphasized.

Nov 7, 2007

jack1234

For this question:
http://tinyurl.com/ynkshx

I just use ma=(3000-800)*20 =44kN to get the answer, and the answer is correct.
and haven't make use of
thrust=exhause velocity * dm/dt
or
change in velocity=exhause velocity*ln|initial mass/final mass|

So, just want to confirm am I solved this problem with correct approach, if not, what is the correct solution?

Physics news on Phys.org

Nov 7, 2007

Dick

Science Advisor

Homework Helper

That's right. It's not really much of a rocket problem, is it?

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...

View full post »

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...

View full post »

Thread 'Explain this asphalt sheen'

This problem is two parts. The first is to determine what effects are being provided by each of the elements - 1) the window panes; 2) the asphalt surface. My answer to that is The second part of the problem is exactly why you get this affect. And one more spoiler:

View full post »