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

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SUMMARY

The discussion centers on calculating the average thrust force exerted by a toy rocket with a mass of 90g, achieving a velocity of 80m/s in 3.0 seconds. Participants established that the average acceleration is 26.667 m/s², and applied Newton's second law to derive the net force. The correct formula for thrust incorporates both the weight of the rocket and the net acceleration, leading to the equation Ft = W + Ma, where W represents the weight of the rocket. This approach clarifies the necessity for thrust to exceed gravitational force for the rocket to ascend.

PREREQUISITES
  • Understanding of Newton's second law of motion
  • Basic knowledge of free-body diagrams
  • Familiarity with calculating weight using W = mg
  • Concept of average acceleration in physics
NEXT STEPS
  • Study the application of Newton's second law in various scenarios
  • Learn how to draw and interpret free-body diagrams
  • Explore the relationship between mass, weight, and gravitational force
  • Investigate the principles of thrust in rocket propulsion systems
USEFUL FOR

Students in physics, educators teaching mechanics, and hobbyists interested in rocketry and basic physics calculations.

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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