- #1
picklepie159
- 19
- 0
Homework Statement
#1.) A rocket exhausts fuel with a velocity of 1500 m/s, relative to the rocket. It starts from outer space with fuel comprising 80 per cent of the total mass. When all the fuel has been exhausted the speed is...
(Answer was 2400 m/s)
Homework Equations
Vrel (dm/dt) = m (dv/dt)
(Does conservation of momentum apply here? I know it applied to an earlier problem, but the velocity of the ejected gasses weren't relative to the rocket)
The Attempt at a Solution
1500 (0.8) = 0.2 v
v = 600 m/s
1500 (0.8) = 1 v
v = 1200... still wrong.
Can anyone help me out here??
Also, if a man in a circular orbit around Earth fires his forward thrusters to drop his KE, would he fall into a larger elliptical orbit with a greater period? It was a question in the book I was confused about.
I know K = -E and E = - GMm/2r , or - GMm/2a