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Flashcards in Lecture 2 Deck (46):
1

Is Andromeda our closest galaxy?

No, it is millions of ly away, outside the Milky Way

2

What kind of object is Andromeda Galaxy?

An Extragalactic object

3

How do we know Andromeda Galaxy will collide with us?

It has a radial velocity coming towards us, and no significant tangential velocity. All the stars we see are blue-shifted, which means they are coming towards us.

4

Will the collision between us and Andromeda include any other galaxies?

Yes, the Triangulum Spiral

5

What will happen to other stars once we collide with Andromeda?

They will not hit each other, but will change their orbits

6

What is the definition of speed?

Rate at which object moves (SCALAR)

7

What is the definition of velocity?

Rate at which object moves in a specific direction (VECTOR)

8

What is the definition of acceleration?

Any change in velocity over time

9

What did Galileo postulate about gravity?

All objects fall at the same rate (ignoring air resistance)

10

What is the definition of Inertia?

A measure of an object's resistance to change in motion

11

What is an inertial frame?

An environment which allows us to estimate motion by observation, e.g. not a moving car, but the Princeton Campus

12

What is Newton's first law of motion?

object in motion will remain in motion unless acted on my a net unbalanced force

13

What is Newton's first law of motion re: momentum?

An object will maintain a constant momentum unless acted upon by an outside force.

14

What is Newton's Second Law of Motion?

F=ma; The acceleration of a body is parallel and directly proportional to the force acting on that body

15

What is Newton's third law of motion?

For every action force, there is an equal opposite reaction force

16

What is the quantity used to represent inertial mass in rotational dynamics?

Moment of inertia

17

What is angular momentum?

rotational velocity x rotational inertia; the measure of how hard it is to stop the rotating body

18

What two factors effect angular momentum?

The distance from the axis and the mass of the rotating body

19

Why do objects move at a constant speed if no force acts on them?

Because momentum is conserved

20

How can the total momentum change?

By an external force acting on the objects

21

How do individual objects change momentum?

Through equal and opposite force (Collisions)

22

What is the parallel of force in rotational dynamics?

Torque

23

Why does the earth not fall into the sun?

Gravitational force is not a torque, so it does not affect the orbit; it only stops the acceleration from allowing Earth to exit the orbit

24

What is a Syzygy?

When three bodies align in a near-straight line

25

What is appulse?

The closest apparent approach of two bodies

26

What is conjunction?

When two bodies are in the same ecliptic plane

27

What is the Greatest Elongation?

WHen one object is furthest from the sun or another object

28

What is Opposition?

The greatest elongation when two bodies are opposite the sun

29

What is a quadrature?

When two bodies make a right angle

30

What is a transit?

When a smaller body passes in front of a larger body

31

What is occultation?

When a larger body passes in front of a smaller body

32

What is an eclipse?

When a body completely/partially disappears from view

33

Which planet has the most angular momentum?

Jupiter

34

What are the two different definitions of weight?

1. gravity pulling down (Pushing up) 2. person's gravity pulls up on the earth (pushing down)

35

How does free-fall occur?

When you have gravity pulling down (Weight 1) and no person's gravity pushing down (weight 2) you are in free-fall

36

What are the two conditions required for an eclipse?

1. a new moon (solar) or full moon (lunar) 2. the moon must be at one of the nodes of its orbit

37

What are the nodes of the moon's orbit?

points where the moon's slightly tilted orbit crosses the earth's ecliptic orbit; happens not quite every six months

38

What are the three main types of energy?

Kinetic, Radiative, Potential

39

What is radiative energy?

Energy that is emitted in the form of light / heat

40

What is the umbra?

The point in an eclipse where the sunlight is completely blocked

41

What is the penumbra?

The point in the eclipse where the sunlight is partially blocked

42

What is the totality?

WHen the sunlight is completely blocked during an eclipse

43

When does a total solar eclipse occur?

When the moon is especially close to the earth, and creates a large shadow

44

When does an annuler eclipse occur?

When the moon is especially close to the earth, and the umbra does not even reach the earth

45

When does a partial solar eclipse occur?

When only part of the sun is blocked

46

What is the Saros Cycle

The calculations used to predict when eclipses will occur