Water Rockets - DSO Amazing Series of Competitions

Water Rockets
Rocket
Nose cone
Plastic bottle
Water
Release
mechanism
Fins
Launch
tube
Bicycle pump
Pressure gauge
Ejected
water
Launcher
Modified from Michael de Podesta & NPL
Types of Rocket
DIY
Commercial
Four forces act on rocket
Centre of Pressure
(CP)
Centre of Gravity
(CG)
Lift
Drag
Thrust
Weight
CP
CG
CG must be in front of CP
CG
CP
©Michael de Podesta & NPL
Finding Centre of Gravity
String
Centre of gravity
©Michael de Podesta & NPL
Finding Centre of Pressure
approximate method
©Michael de Podesta & NPL
Simple Rocket Design
©Michael de Podesta & NPL
Launching the Rocket
No support for rocket
Launch
Tube
Launch
Ramp
©Michael de Podesta & NPL
18 g acceleration
Water Rocket Physics
Newton’s 1st Law
Weight
Net Thrust
A body stays at rest or in
uniform motion unless
acted upon by a force.
Thrust
Newton’s 2nd Law
mass m2
velocity v2
Force is equal to the
change in momentum
per change in time.
m2v 2  m1v1
F
dt
unit
change
in time
dt
Net Thrust
F
mass m1
velocity v1
m2 is smaller than m1
v2 is greater than v1
Newton’s 3rd Law
Air pressure pushes
water backward
For every action there
is an equal and
opposite reaction.
Water pushes
rocket forward
Sign up now to build and fire your
own water rocket at the SAFMC and
win attractive prizes!
Date: 19 March 2011
Email: safmc@science.edu.sg