Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pulsejet engine dynamics in vertical motion using momentum conservation   The momentum conservation law is applied to analyse the dynamics of pulsejet
engine in vertical motion in a uniform gravitational field in the absence of
friction. The model predicts existence of a terminal speed given frequency of
the short pulses. The conditions that the engine does not return to the
starting position are identified. The number of short periodic pulses after
which the engine returns to the starting position is found to be independent of
the exhaust velocity and gravitational field intensity for certain frequency of
the pulses. The pulsejet engine and turbojet engine aircraft models of dynamics
are compared. Also the octopus dynamics is modelled. The paper is addressed to
intermediate undergraduate students of classical mechanics and aerospace
engineering.

2
The categories of this paper are: math
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat