Download Bottle Rockets `08

Bottle Rockets ‘08
Shooting for the Stars
Contents
 Yes, it is Rocket Science –
physics concepts
 Construction tips
 Video examples
Rocket Physics
 Forces, FBD’s
 Newton’s Laws
 1 - Inertia
 2 - a=F/m
 3 - Action force and reaction force
 Conservation of Momentum
 Conservation of Energy
Forces
 What forces might be acting on the
rocket at various moments in its flight?
 Draw arrows on the blank FBD’s to indicate
all the forces on the rocket
Newton’s 1st Law
 Inertia
 An object at rest remains at rest unless acted
upon by an external force
 Net force causes acceleration
 Weight downward and normal force upward
are equal while on launchpad
 Until you pull the trigger…
Newton’s 3rd Law
 For every action force there is an equal
and opposite reaction force
 When the trigger is pulled, the bottle pushes
water downward. This is the Action force
 The reaction force? The water pushes the
bottle upward.
 The downward force on the water and the
upward force on the bottle are equal in
magnitude (strength)
 What is the effect of this force on the
bottle?...
Newton’s 2nd Law
 a = F/m
 With the force of the water pushing it
upward, the bottle accelerates.
 What determines how fast the bottle
accelerates?
 The bottle’s mass – less mass, greater acceleration
 The force from the water – more pressure inside,
greater acceleration
Conservation of Momentum
 The total momentum of a system is
conserved
 Total momentum before =
total momentum after
 Before: both water and rocket are at rest
 Total momentum = 0 kg m/s
 After: water moving downward, bottle
moving upward
 Total momentum still = 0 kg m/s
Conservation of Energy
 Energy flow diagram:
EPEKEGPEKEheat, sound
KE
EPE
sound
GPE
KE
Sound,
heat
Conservation of Energy
 Elastic Potential Energy
 Waiting on launch pad, bottle under pressure
  KE
 Moving fast!!! During launch
  Gravitational PE
 Getting higher, but slowing down
  KE
 Falling faster
  heat, sound
 Parachutes friction with air slows bottle
down, makes noise
Construction Tips
 http://www.tclauset.org/21_BtlRockets/B
TL.html
 http://en.wikipedia.org/wiki/Water_rocke
t
 http://members.aol.com/hayhurst1/h2or
ocket.htm
Examples
 Youtube video of 2008 launches