AST201 Lecture 3 Notes.docx

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Astronomy & Astrophysics
Stephen Reid

LECTURE 3 41451 What is motion It is movementCAR EXAMPLE2 Speed How far it will go in a certain amount of time 20 km 1min3 VelocityHow fastslow it will go and towards what direction 20km north 4 Acceleration If car is changing velocity speed Than it is called accelerationACCELERATION OF GRAVITY5 Galileo He found that gravity accelerates all objects at the same rateamounttime regardless of how much they weightmass For example in the moon where there is no gravity if a feather and rock are dropped than they will land at the same time no gravity 6 The example above is Acceleration of GravityThe movementacceleration of a falling object7 At what speed do falling objects fall This is pretty obvious Gravity in earth makes it 10meterssecond squared Basically if you drop a pencil than the pencil at the starting point is at 0ms Than after 1 second it is at 10ms than at 2 seconds it is a20ms Therefore the speed of falling will only increase8 Momentum Product of mass and velocity2 objects Momentummassvelocity The only way to change an objects momentum is to add force to itIts basically the quantity of motion force IeIf a bug hits you at the same speed as a truck what will affect your car more Bug or Truck Obviously the truck Therefore the truck gives more momentum than the fly to your carChange in momentum occurs when the netforce is not zeroit is as zero when the car is at constant velocity9 Netforce Overall force An object is accelerating when net force is not zeroWHAT DO PLANETS HAVE TO DO WITH THIS ACCELERATION JACK SHITWell Planets are always accel they are constantly moving and there is this net force that is causing them to orbit the sun and move the direction they do Isaac Newton discovered what this thing was GRAVITYIF YOU DROP 2 BALLSA MARBLE AND A BASKETBALL WITH SAME MASS FROM SAME HIEGHT BASKETBALL WILL TAKE SLIGHTLY LONGER BECAUSE AIR RESISTANCE SLOWS IT DOWN MORE BASED ON ITS SIZE 1 Mass amount of matter in your body 2 Weight Depends on your body weight and mass and gravity of forcelike when you are on a lift and the lift is at the stop your weight is normal but when lift moves up your weight is more but when lift moves down your weight is less DIFFERENCE BETWEEN MASS AND WEIGHT Mass stays the same but weight can varyyour mass will be same on earth even if you are on the moon but your weight will be different on the moons since the moon has weaker gravityTake the elevator example into action now imagine the elevator got busted and it is automatically shaking all over the place the netforce of you would be 0 since you are floating There fore your mass will remain the same but you will be weightless since your feet is not on the floorfree fall Astronauts in space are weightless because they are in free fall mode They do not have their feet on the ground 3 Freefall When peopleobjects are weightless when they are falling or when they are weightlessNEWTONS LAW OF MOTION 4 AristotleNewtonShow down time Aristotle went down the outer orbits that Aristotle thought were heavens were not really heavensNewton killed Aristotles dumb theory by stating that gravity exists in Aristotles heaven and that the heaven is a part of our universe5 Astrophysics Newton Came up with that shit the physical phenominas on earth also exist in the cosmos6 NEWTONS THREE LAWS OF MOTION a An object remains at its constant velocity until a netforceacts to change its speeddirection b ForceMassAcceleration c For any force there is always an equal or opposite reaction force important to astro because planets always have a force pushing them towards each other gravity7 Conservation of Momentum This law tells us that the momentum of all objects interacting remain the same two balls colliding An object can only gainloose a momentum when a force causes it to exchange momentums with one another
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