Transcript Rocket Physics

ROCKET PHYSICS
Summarize from launch to
landing. Vocab words as
applied to our rocket
activity
APPLY THESE IDEAS IN YOUR
SUMMARY
inertia, gravity,
fluid friction,
acceleration, air
resistance,
momentum,
Newton’s Laws,
action/reaction
pairs,
unbalanced
forces, Boyle’s
Law.
FRICTION
• Friction- a force that works against motion (possible
because of pressure, unevenness)
• The bottle screw top threads give us the uneven
surface so we can have static friction holding the
rocket in place.
• When the rocket travels through the air it has fluid
friction – also known as air resistance. This is
determined by surface shape, area and texture
GRAVITY
• Gravity- Inertia (mass), and distance. For the whole
process there is gravity. How does it help or hurt the
motion of the rocket?
• With a real rocket, how would the distance change
the gravity?
• How does the mass affect your decision about the
amount of water in the rocket?
MOMENTUM
• Momentum= Mass X Velocity.
• How will you change the velocity so that the rockets
will have less momentum?
• What force always works against motion? Friction
• Think big truck hitting you vs. bike hitting you and
you understand momentum. How can the speed of
the bike or the truck also matter as well as the
mass?
MOMENTUM EXAMPLES
• We talked about how the bad guy can jump off the
second floor and land in the dumpster and be OK, but if
he is running from the cops and jumps off the 5th floor ,
he is not OK. If gravity stays the same, because his mass
is the same, then what changed? …. His speed of falling,
Objects get faster and faster as they fall until they reach
terminal velocity. 9.8 meters per second per second is
the rate our falling speed increases.
• We talked about how downhill ski racers position
themselves in a tight tuck to reduce AIR RESISTANCE and
bike racers also get low over the bars, and race cars are
designed with a sleek front – all to avoid air resistance
which is a kind of fluid friction and ALL friction works
against MOTION.
INERTIA
• Inertia (mass)- stubbornness- Newton # 1
• Newton’s 1st Law Rest/motion/unbalanced
• An object at rest and an object in motion will
remain unchanged until acted upon by an
UNBALANCED force.
• What forces (balanced or unbalanced) are acting
on your rocket? Do these forces change? How?
NEWTON’S 3RD
LAW
• Newton’s 3rd Law – reaction/reaction, equal and
opposite actions.
• Every action has an equal and opposite reaction.
• The gas under pressure (remember Boyle’s Law)
pushes the ground and the ground pushes back.
The creates the unbalanced force so that the net
force is UP.
AIR RESISTANCE
• Parachute= increased air resistance
• More surface creates more fluid friction and this will
slow the rocket to create a reduced velocity
(speed and direction)
• How will air resistance be a help or a problem with
your rocket?
PRESSURE= FORCE /AREA
• Big area= little pressure , think tennis shoes vs. high
heels – which ones let you sink in the lawn? You
have not changed your weight (the FORCE of
gravity) but your area over which you exert this
force changes.
• Why a point on the top of the rocket? How does
this change the pressure for the rocket to press
through the air?
NEWTON’S 2ND
LAW
• Acceleration= Force divided by Mass
• Force= Acceleration X Mass
Think the force of the big truck Mass) when moving
at different speeds (acceleration) and hits you.
• Newton is the unit for force
• Newton saw an apple fall from a tree and so he
named it gravity.
FORCE/NEWTON
• You can find the net force by: adding forces in the
same direction and subtracting forces in opposite
directions
• When we pushed on the table together in the same
direction, we ADDED our forces together. When we
pushed in opposite directions we subtracted our
forces. IF there was no movement then we knew
our forces were BALANCED, had we subtracted the
answer would have been ZERO. This was a
balanced force.
• UNBALANCED forces create movement.