Rocket dynamics

  • Thread starter icymage
  • Start date
  • #1
icymage
2
0
The weight of a rocket is 80kN at the instant it takes off , and the products of the combusion are ejected at a velocity of 0.60 kms-1 relative to the rocket. Calculate the rate at which the rocket must be consuming fuel in order to take off vertically. Ans: 134kgs-1

Cant find a solution despite numerous attempt , anyone can help ?
 

Answers and Replies

  • #2
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,624
8
Welcome to PF icymage,

Could you perhaps detail your attemps to that we can see where your going wrong?
 
  • #3
icymage
2
0
hmm i tried using the equation f = m(dv/dt) + v (dm/dt) and p = mv and i can't get the answer. Anw this isn't coursework/schoolwork it is a question i stumbled upon on a old textbook of mine.
 
  • #4
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,624
8
hmm i tried using the equation f = m(dv/dt) + v (dm/dt) and p = mv and i can't get the answer. Anw this isn't coursework/schoolwork it is a question i stumbled upon on a old textbook of mine.
Take a look at this excellent https://www.physicsforums.com/showthread.php?t=199087" by D_H, and see if it helps clarify things.
 
Last edited by a moderator:
  • #5
tiny-tim
Science Advisor
Homework Helper
25,838
255
Welcome to PF!

hmm i tried using the equation f = m(dv/dt) + v (dm/dt) and p = mv and i can't get the answer.

Hi icymage! Welcome to PF! :smile:

This isn't really a caluclus question … it would be if you were asked to find the fuel used to reach a certain time, for example … but you're only asked for the initial fuel used while the speed is zero.

Hint: how much acceleration does the fuel have to produce before the rocket lifts off?

how much mass and velocity produce that acceleration? :smile:
 

Suggested for: Rocket dynamics

  • Last Post
Replies
14
Views
424
  • Last Post
Replies
8
Views
384
Replies
1
Views
494
Replies
5
Views
130
  • Last Post
Replies
30
Views
751
Replies
3
Views
342
  • Last Post
Replies
1
Views
216
  • Last Post
Replies
4
Views
417
Replies
12
Views
618
Top