Read about rocket motion | 4 Discussions | Page 1

  1. Physyx

    How to model a rocket equation from the derivative of momentum?

    I am using the derivative of momentum (dp/dt) with Newton’s 3rd Law with the gravitational force of Earth. F - [Force of gravity on rocket] = dp/dt F - (G * m_e * m_r / r2 ) = v * dm/dt + ma F = Force created by fuel (at time t) G = Gravitational Constant m_e = Mass of Earth m_r = Mass of...
  2. bob14

    Error When Deriving the Rocket Equation

    Homework Statement I want to try to derive the rocket equation and then add additional effects like gravity, air resistance, etc. Here's the equation that I found online: Homework Equations p (momentum) = mass * velocity F (force) = Δp / Δt The Attempt at a Solution [/B] pi = mv Here...
  3. Dopplershift

    Rocket's Initial Mass

    The problem states: Typical chemical fuels yield exhaust speeds of the order of 103 m/s. Let us imagine we had a fuel that gives v0 = 3 × 105 m/s. What initial mass of fuel would the rocket need in order to attain a final velocity of 0.1c for a final mass of 1 ton? I derived the equation in the...
  4. J

    Rocket motion under gravity

    Homework Statement A rocket with initial mass of m0. The engine that can burn gas at a rate defined by m(t)=m0-αt, and expel gas at speed (relative to the rocket) of u(t)=u0-βt. Here, m0, α, u0, and β are all constants. Assume the lift-off from ground is immediate a) The rocket speed v(t)=...