Accelerating force due to ejection

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SUMMARY

The discussion focuses on calculating the accelerating force of a festival rocket ejecting 0.05 kg of gases per second at a velocity of 400 m/s. The relevant formula is F = dp/dt, derived from Newton's second law, which states that the net force is equal to the rate of change of momentum. In this case, momentum (p) is defined as mass (m) times velocity (v), leading to the equation F = d(mv)/dt. Since the mass of the rocket changes during ejection, the full form of the equation must be applied.

PREREQUISITES
  • Understanding of Newton's second law of motion
  • Basic knowledge of momentum (p = mv)
  • Familiarity with calculus concepts, specifically derivatives
  • Knowledge of rocket propulsion principles
NEXT STEPS
  • Study the derivation of F = dp/dt in detail
  • Explore the implications of changing mass in rocket propulsion
  • Learn about the thrust calculation for rockets using the Tsiolkovsky rocket equation
  • Investigate real-world applications of Newton's laws in aerospace engineering
USEFUL FOR

Students of physics, aerospace engineers, and anyone interested in the principles of rocket propulsion and dynamics will benefit from this discussion.

Jowin
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A festival rocket is ejecting 0.05 kg of gases per second at a velocity 400m/s The accelerating force on the is? The formula given in the book is F=dp/dt What does the formula mean:confused:
 
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Jowin said:
A festival rocket is ejecting 0.05 kg of gases per second at a velocity 400m/s The accelerating force on the is? The formula given in the book is F=dp/dt What does the formula mean:confused:
The formula is known as Newton's second law and states that the net force acting on a body is equal to the rate of change of the [linear] momentum of the body.
 
Last edited:
Welcome to PF!

Hi Jowin! Welcome to PF! :smile:
Jowin said:
A festival rocket is ejecting 0.05 kg of gases per second at a velocity 400m/s The accelerating force on the is? The formula given in the book is F=dp/dt What does the formula mean:confused:
Hootenanny said:
The formula is known as Newton's second law and states that the net force acting on a body is equal to the rate of change of the [linear] momentum of the body.

I'll just add:

p is momentum, which is mass times velocity: p = mv.

F = dp/dt is the official version of good ol' Newton's second law …

so it's F = d(mv)/dt = m dv/dt + v dm/dt, which for fixed m is F = m dv/dt, which is probably what you recognise. :wink:

But for space rockets and festival rockets, m changes, so the official version has to be used! :biggrin:
 

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