Astronomy 101 The Solar System Tuesday Thursday 2

Astronomy 101 The Solar System Tuesday, Thursday 2: 30 -3: 45 pm Hasbrouck 20 Tom Burbine tomburbine@astro. umass. edu

Course • Course Website: – http: //blogs. umass. edu/astron 101 -tburbine/ • Textbook: – Pathways to Astronomy (2 nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator.

Office Hours • Mine • Tuesday, Thursday - 1: 15 -2: 15 pm • Lederle Graduate Research Tower C 632 • Neil • Tuesday, Thursday - 11 am-noon • Lederle Graduate Research Tower B 619 -O

Homework • We will use Spark • https: //spark. oit. umass. edu/webct/logon. Display. d owebct • 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/astron 101 -tburbine

Exam #1 • • • Review questions are online Thursday 40 questions Multiple choice and True/False Review session: – Wednesday 6 -7 pm in Hasbrouck 20

http: //www. hulu. com/watch/63319/cosmos-the-harmony-of-the-worlds

Acceleration • Acceleration is when your velocity is changing • Velocity not changing, no acceleration

Acceleration • • • 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/s 2

Difference 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

Isaac Newton (1642 -1727) • 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 Motion

Force • Force – anything that can cause a body to change velocity

Newton’s st 1 Law • 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 it

Why do things on Earth not remain in motion?

Why do things on Earth not remain in motion? • Friction

Newton’s • • • nd 2 Law Force = mass x acceleration Units of Force kg m/s 2 = newton So much do you weigh Say your mass is 100 kg F = 100 kg x 9. 8 m/s 2 F = 980 Newtons

Newton’s rd 3 Law • 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 force

http: //www. vshiksha. com/system/files/u 1/pslvc 6 -rocket. jpg

Newton’s Universal Law of Gravitation • Every mass attracts every other mass through the force called gravity • Newton came up with this formula F = G M 1 M 2 r 2 M 1, M 2 are the masses of the two objects r is the distance between the objects G = constant = 6. 67 x 10 -11 m 3/(kg s 2)

So what should you know about this formula F = G M 1 M 2 r 2 • 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 number

What is the attraction of two people in this room? F = G M 1 M 2 r 2 • • • Say their masses are both 100 kg Their distances are 10 meters apart F = 6. 67 x 10 -11 m 3/(kg s 2) * 100*100 kg 2/(10*10 m 2) F = 6. 67 x 10 -9 N = 0. 000067 N Remember the person weighs 980 N

Any Questions?