Calculate Rocket Thrust Force of 90g Rocket Achieving 80m/s in 3.0s

AI Thread Summary
To calculate the average thrust force of a 90g rocket achieving 80m/s in 3.0 seconds, the average acceleration is determined to be 26.667 m/s². The net force is calculated using Newton's second law, where thrust must exceed the weight of the rocket to achieve upward acceleration. The formula used is Ft - W = Ma, where W represents the weight of the rocket. Participants emphasize the importance of considering gravitational force in the calculations. Understanding these principles is crucial for accurately determining the thrust force required for the rocket's ascent.
Sucks@Physics
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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
 
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Can you find the average acceleration?
 
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:
avg acceleration = 26.667m/s and lol yea its on earth
 
no help?
 
Sucks@Physics said:
avg acceleration = 26.667m/s and lol yea its on earth

Acceleration is in m/s^2.

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

Fnet = (m*v)/t

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

What did i do wrong?
 
Am i not supposed to be solving for Fnet?
 
Can some1 help i ahve to have this finished by tomorrow and I'm doing it wrong
 
  • #10
Does it give you a rate at which the mass of the rocket is changing?
 
  • #11
I think I'm neglecting that.
 
  • #12
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
aq1q said:
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
What force must the rocket thrust counteract in order for the rocket to rise?
 

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