Orbits and the Wider Universe 4.3

Question 1

define Kepler 1st law?

Answer 1

The orbit of a planet is an ellipse with the Sun at one focus.

Question 2

Define Kepler 2nd law?

Answer 2

The line joining the planet to the sun sweeps out equal areas in equal intervals of time.

Question 3

Define Kepler 3rd Law?

Answer 3

The square of the period (T) of the orbit is proportional to the cube of the semi-major axis (a) of its orbit.

(T^2 directly proportional to a^3)

Question 4

relateing to any elliptical orbit.

Answer 4

T^2 = 4 pi^2a^3/GM

Question 5

Energy of an object in elliptical orbit equation?

Answer 5

E = -1/2 GMm/a

Question 6

finding speed for any circular orbit.

Answer 6

V^2 = GM/r

Question 7

define a rotation curve?

Answer 7

a plot of orbital velocity against distance from the centre for an astronomical system.

Question 8

Rotation curve has this simple form because?

Answer 8

1. The Sun contains great bulk of mass in solar system.
2. The Solar System objects outside the sun
3. The Sun is almost spherically symmetrical.

Question 9

Define Nonbaryonic matter?

Answer 9

matter which is not composed of quarks + leptons but interacts with the gravitational force.

(Main component of dark matter. )

Question 10

Define radial velocity?

Answer 10

component of its velocity relative to an observer on earth.

Question 11

How is the position of the centre of mass calculated for 2 small objects?

Answer 11

M1R1 = M2R2

M = mass
R = Radius

Question 12

define a exoplanet?

Answer 12

a planet which orbits a star other than the sun.What

Question 13

What does Hubble’s law state?

Answer 13

Recession Velocity of deep space objects is proportional to their proper distance.

Question 14

Hubble’s law equation?

Answer 14

v = HD

v = velocity
H = hubbles constant
D = Distance

Question 15

The Hubble time?

Answer 15

estimate of the age of the universe and is defined as the reciprocal of the Hubble constant.