Rocket Thrust Force

  • #1
A toy rocket, of mass 90g, acheives a velocity of 80m/s after 3.0s when fired straight up. What average thrust force does the rocket engine exert?

I dont' know what formula to use for this
 

Answers and Replies

  • #2
hage567
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Can you find the average acceleration?
 
  • #3
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is this held in earth where gravity exists? lol, i know its a dumb question, but sometimes during my life, i have done problems like these without the involvement of gravity.
 
Last edited:
  • #4
avg acceleration = 26.667m/s and lol yea its on earth
 
  • #6
hage567
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avg acceleration = 26.667m/s and lol yea its on earth

Acceleration is in m/s^2.

So what's Newton's second law?
 
  • #7
what i did is...

Fnet = (m*v)/t

Fnet = (.09*80)/3 = 2.4N

What did i do wrong?
 
  • #8
Am i not supposed to be solving for Fnet?
 
  • #9
Can some1 help i ahve to have this finished by tomorrow and i'm doing it wrong
 
  • #10
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Does it give you a rate at which the mass of the rocket is changing?
 
  • #11
I think i'm neglecting that.
 
  • #12
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ok, start out by drawing a free-body diagram. since the thrust is accelerating upwards.. thrust must me greater than weight. therefore Ft-W=Ma soo Ft=w+ma, right?

Solve for a, and then just plug and chug..
 
  • #13
sweet thanks, i get it now
 
  • #14
ok, start out by drawing a free-body diagram. since the thrust is accelerating upwards.. thrust must me greater than weight. therefore Ft-W=Ma soo Ft=w+ma, right?

Solve for a, and then just plug and chug..

hey, i have the same question, but what does w stand for? since m = mass, Ft = force of thrust anf a = acceleration (right)? then what is w?
 
  • #15
SteamKing
Staff Emeritus
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What force must the rocket thrust counteract in order for the rocket to rise?
 

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