# What is Rocket problem: Definition and 33 Discussions

A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordance with Newton's third law. Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Vehicles propelled by rocket engines are commonly called rockets. Rocket vehicles carry their own oxidizer, unlike most combustion engines, so rocket engines can be used in a vacuum to propel spacecraft and ballistic missiles.Compared to other types of jet engines, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest specific impulse). The ideal exhaust is hydrogen, the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity.Rocket engines become more efficient at high speeds, due to the Oberth effect.

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1. ### Water Rocket Science Project by Tanguy: Reach 11,2k m/s!

Hi ! I'm a French student in Terminale (12th grade equivalent) and I have to do an oral presentation of 5min (Grand Oral) for my baccalauréat linked with my professional project. As I want to become an engineer in astrophysics, I want to talk about water rocket and the theoretical possibility to...
2. ### Rocket problem -- separated fuel tank in free fall

I know that this should be a very simple problem, but I don't understand how to solve it without knowing the height at which the tank is separated from the rocket. I will be very grateful for any hint.
3. ### Solve Rocket Problem with Step-by-Step Guide | Imaginary Number Solution

This is what I tried and it makes perfect sense to me. When i plug in the numbers to what I ended up with, I get an imaginary number for U initial... Work is attached below.
4. ### Rocket Problem -- Solve using the Rocket Equation

I tried the second rocket equation vf = vi + v rel * ln(Mi/Mf) but it gives out approximately 4900 m/s for the answer but the answer is 4160 m/s
5. ### 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 is...
6. ### Rocket subject to linear resistive force -- two methods

Homework Statement Consider a rocket subject to a linear resistive force, $$f = -bv$$, but no other external forces. Use Equation (3.29) in Problem 3.11 to show that if the rocket starts from rest and ejects mass at a constant rate $$k = -\dot{m}$$, then its speed is given by: v =...
7. ### Newton's Second Law Rocket Problem

Homework Statement A person whose mass is 20 kg needs to accelerate vertically from the surface of the Earth at 5.0m/s^2 and is trying to pick which rocket he should strap to his back. How much thrust does he need if each rocket has a mass of 30 kg? Homework Equations F=ma The Attempt at a...
8. ### Special Relativity - Rocket problem (particle mechanics)

Problem statement: A rocket propels itself rectilinearly by giving portions of its mass a constant (backward) velocity ## u ## relative to its instantaneous rest frame. It continues to do so until it attains a velocity ## v ## relative to its initial rest frame. Prove that the ratio of the...
9. ### Calculating Angular Momentum Reduction in Rotating Rockets

how do i calculate the gradual reduction of angular momentum a rocket initially has before it fires its main rocket engines? I am assuming if the thrust is high enough then the rocket should eventually stop rotating and travel in a straight line. assume the rocket is in a universe without...
10. ### Kinematics Rocket Problem

Homework Statement A 25 kg Rocket generates 400 N of thrust. It is designed to burn its fuel for 40 seconds. If launched vertically what will its final vertical velocity be when the fuel runs out? How high can it fly? How long until it reaches the ground? Neglect mass of fuel, and air...
11. ### Calculating Rocket Energy in Satellite Orbit Problem

Assume that a satellite(mass m) is orbiting the Earth(mass M) at radius R and speed V (the orbit is circular). The satellite is in a position such that the force of gravity exerted on it by the planet is not enough to keep it in orbit. Therefore, the satellite has an engine, which always points...
12. ### Rocket Velocity and Acceleration Calculation: A Step-by-Step Guide

Homework Statement Consider a rocket in space that ejects burned fuel at a speed of v_ex= 2.0 km/s with respect to the rocket. The rocket burns 10 % of its mass in 340 s (assume the burn rate is constant). (a) What is the speed v of the rocket after a burn time of 170.0 s? (suppose...
13. ### Rocket Problem: Determining the amount of fuel burned

The set up: A 20,000kg rocket has a motor that generates a thrust of 3x10^5 N. The problem: a)What is it's initial Acceleration? b)At an altitude of 5,000m the rockets acceleration has increased to 6 m/s^2, what mass of fuel has it burned? Relevant equations: F = ma The...
14. ### Projectile Motion Rocket Problem

Homework Statement Please check my work A model rocket is launched vertically upwards with an initial speed of 50m/s. It accelerates with a constant upward acceleartion of 2m/s until its engine stop at an altitude of 150m. 2.4.1) What is the maximum height reached by the rocket...
15. ### Maximizing Rocket Height at 1km Altitude: Solving for Acceleration and Time

I know I've done this problem a few times before but I'm just a fumbling idiot at the moment.. Homework Statement Rocket has an acceleration of 12m/s^2 and at an altitude of 1km the motor shuts off. What is the maximum height? Homework Equations V^2=V_i+2a(x_f-X_i)...
16. ### Vertically launched rocket problem with integration

Homework Statement Find the Rockets height as a function of time It is in a constant field g. u refers to the exhaust speed and M is the initial mass. Starts from rest. and is single stage. Homework Equations 1) m * dv/dt= -dm/dt * u-mg 2)Show that height as t is: y(t)= u*t- 1/2*g*t^2-...
17. ### Rocket Problem: Kinematics Answer Doesn't Make Sense?

Homework Statement A rocket, initially at rest on the ground, accelerates straight upward from rest with constant acceleration 34.3 m/s^2. The acceleration period lasts for time 10.0 s until the fuel is exhausted. After that, the rocket is in free fall. Find the maximum height y_max...
18. ### Rocket Problem: Finding Velocity of Rocket as Function of Time

Homework Statement A rocket ascends from rest in a uniform gravitational field by ejecting exhaust with constant speed u. Assume that the rate at which mass is expelled is given by dm/dt = km, where m is the instantaneous mass of the rocket and k is a constant, and that the rocket is retaded...
19. ### Rocket Problem: Solving for Velocity, Time, and Altitude

Rocket Problem, please help :) Homework Statement A rocket rises vertically, from rest, with an acceleration of 3.2 m/s^2 until it runs out of fuel at an altitude of 950 meters. After this point, it's acceleration is that of gravity, downward. a) What is the velocity of the rocket when it runs...
20. ### Kinematics toy rocket problem

Homework Statement A toy rocket moving vertically upward passes by a 2.2 m high window whose sill is 9.0m above the ground. The rocket takes 0.17s to travel the 2.2m height of the window. What was the launch speed of the rocket, and how high will it go? Assume the propellant is burned very...
21. ### Goldstein's Rocket problem.

Homework Statement Given a rocket that is accelerating upward until escape velocity, find m_gas/m_rocket. Should be near 300, I'm getting 6.5.Homework Equations The Attempt at a Solution Here's a pdf in google docs...
22. ### Special Relativity Rocket Problem

1. Two rockets, A and B, leave a space station with velocity vectors va and vb relative to the station frame S, perpendicular to each other. (a) Determine the velocity of A and to B, vba. (b) Determine the velocity of B relative to A, vab. (c) Explain why vab and vba do not point in...
23. ### Rocket problem: Newton's 2nd Law

Homework Statement In this problem we explore a slightly more realistic model of a rocket's acceleration still neglecting air resistance. Consider a rocket fired straight up from rest burning fuel at the constant rate of b kg/s. Let v=v(t) be the velocity of the rocket at time t and suppose...
24. ### Rocket problem (time is wrong )

rocket problem (time is wrong!) Homework Statement A test rocket is fired vertically upward from a well. A catapult gives it an initial speed of 80.0 m/s at ground level. Its engines then fire and it accelerates upward at 4.00 m/s^2 until it reaches an altitude of 1000m. At that point its...
25. ### Kinematics Plane and Rocket Problem

Homework Statement Some plane is flying at an altitude of 12.0 km above sea level and is flying in a straight line at 850km/h. The plane then drops a rocket. After the drop the plane maintains the same altitude and speed and continues to fly in a straight line. The rocket falls for a brief...
26. ### Kinematics Model Rocket problem

Kinematics Model Rocket problem ! A) A model rocket is launched straight upward with an initial speed of 49.6 m/s. It accelerates with a constant upward acceleration of 1.83 m/s2 until its engines stop at an altitude of 155 m. What is the maximum height reached by the rocket? B) How long...
27. ### What is the net force on a weather rocket during its flight?

Homework Statement A small rocket to gather weather data is launched straight up. Several seconds into the flight, its velocity is 120 m/s and it is accelerating at 18 m/s^2. At this instant, the rocket's mass is 48 kg and it is losing mass at the rate of .5 kg/s as it burns fuel. What is...
28. ### Calculus Rocket Problem (Derivatives)

Homework Statement A model rocket is launched vertically upward. If it's position (height) y above the ground in feet as a function of time t in seconds is given by: Homework Equations y = f(t) = 192t - 16t^2 The Attempt at a Solution 1. Find the instantaneous velocity and...
29. ### Two stage Rocket problem

Homework Statement In the first stage of a two stage rocket, the rocket is fired fro, the launch pad starting from rest but with a constant acceleration of 3.50 m/s^2 upward. At 25.0 s after launch, the rocket fires the second stage, which suddenly boosts its speed to 132.5 m/s upward. This...
30. ### Projectile motion rocket problem

Homework Statement A rocket is fired at at speed fo 75.0 m/s from ground level, at an angle of 60.0 deg. above the horizontal. The rocket is fired toward an 11.0 m high wall, shich is located 27.0 m away. The rocket attains its launch speed in a negligibly short period of time, after...
31. ### Need help with rocket problem

Hello, I am having an awfully hard time working out this rocket problem. Say you want to have a 2D representation of a rocket launching from the earth, either it will crash right away, have a decaying orbit or a stable orbit. If you launch a rocket at, say, 88 degrees it will have a...
32. ### Rocket Problem - Law Of Conservation Of Momentum

Hi, I am unable to solve this problem. :zzz: I applied Law of Conservation of Momentum but unable to get the related answer. The problem is as. :!) "A rocket is moving vertically upward. % Kg fuel gas is released out of it in downward direction with a velocity of 5000 m/s. If the...
33. ### Rocket Problem: 0.27kg Mass, 0.18kg Gas, 40m/s Velocity

First the rocket doesn't move. Its initial mass is 0,27 kg. Then the rocket starts to emit gases. During one second it emits 0,09kg gas with velocity in system of rocket of 300m/s. How much time does it takes for rocket to receive 40m/s velocity and what is the max velocity a rocket can get when...