Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine [email protected] CourseOffice HoursHomeworkHW #2, #3, #4Exam #1Slide Number 7AccelerationAccelerationDifference between mass and weightIsaac Newton (1642-1727)ForceNewton’s 1st LawWhy do things on Earth not remain in motion?Why do things on Earth not remain in motion?Newton’s 2nd LawNewton’s 3rd LawSlide Number 18Newton’s Universal Law of GravitationSo what should you know about this formulaWhat is the attraction of two people in this room?Any Questions?Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom [email protected]• Course Website:– http://blogs.umass.edu/astron101-tburbine/• Textbook:– Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny.•You also will need a calculator.Office Hours• Mine• Tuesday, Thursday - 1:15-2:15pm•Lederle Graduate Research Tower C 632• Neil• Tuesday, Thursday - 11 am-noon • Lederle Graduate Research Tower B 619-OHomework• We will use Spark•https://spark.oit.umass.edu/webct/logonDisplay.dowebct• Homework will be due approximately twice a week•I will drop the lowest homework score.HW #2, #3, #4• I will go over the answers• http://blogs.umass.edu/astron101-tburbineExam #1• Review questions are online• Thursday• 40 questions• Multiple choice and True/False• Review session:– Wednesday 6-7 pm in Hasbrouck 20http://www.hulu.com/watch/63319/cosmos-the-harmony-of-the-worldsAcceleration• Acceleration is when your velocity is changing• Velocity not changing, no accelerationAcceleration• a = ∆v/∆t• Car is travelling at 10 m/s• Increases its speed to 30 m/s over 5 seconds• a = (30 m/s – 10 m/s)/5 seconds•a = 4 m/s2Difference between mass and weight• Mass is the amount of matter in your body• Weight is the amount of force acting on your body• So on the Moon, you would have the same mass as on Earth but weigh less on the Moon since the Moon is less massive than Earth• Supposedly saw an apple fall to the ground• He then understood that gravity was universal, meaning it affected both the planets and us on Earth• Came up with 3 Laws of MotionIsaac Newton (1642-1727)Force• Force – anything that can cause a body to change velocityNewton’s 1stLaw• In the absence of a net (overall) force acting upon it, an object moves with a constant velocity• An object at rest remains at rest• An object in motion tends to remain in motion unless a force is acting upon itWhy do things on Earth not remain in motion?Why do things on Earth not remain in motion?• FrictionNewton’s 2ndLaw• Force = mass x acceleration• Units of Force kg⋅m/s2= newton• So much do you weigh• Say your mass is 100 kg• F = 100 kg x 9.8 m/s2• F = 980 NewtonsNewton’s 3rdLaw• For any force, there is an equal and opposite reaction force• Gravity is holding you on the ground•The ground is also pushing back up on you with the same amount of forcehttp://www.vshiksha.com/system/files/u1/pslvc6-rocket.jpgNewton’s Universal Law of Gravitation• Every mass attracts every other mass through the force called gravity• Newton came up with this formulaF = G M1M2r2M1, M2 are the masses of the two objectsr is the distance between the objectsG = constant = 6.67 x 10-11 m3/(kg⋅s2)So what should you know about this formulaF = G M1M2r2• The force of attraction between any two objects is directly proportional to the product of their masses• The force of attraction between two objects decreases with the square of the distance between their centers• G is a very small numberWhat is the attraction of two people in this room?F = G M1M2r2• Say their masses are both 100 kg• Their distances are 10 meters apart• F = 6.67 x 10-11 m3/(kg⋅s2) * 100*100 kg2/(10*10 m2)• F = 6.67 x 10-9N = 0.0000000067 N• Remember the person weighs 980 NAny
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