ROCKET PHYSICS Summarize from launch to landing. Vocab words as applied to our rocket activity
inertia, gravity, fluid friction, acceleration, air resistance, momentum, Newton’s Laws, action/reaction pairs, unbalanced forces, Boyle’s Law. APPLY THESE IDEAS IN YOUR SUMMARY
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.