Units 11-15

Question 1

retrograde motion

Answer 1

planets moving west to east, its path through the stars zig zags or loops

Question 2

geocentric model

Answer 2

belief that stars and planets moved around earth

Question 3

epicylces

Answer 3

small circles proposed to explain retrograde motion in geocentric model

Question 4

occam’s razor

Answer 4

when we begin with incorrect assumptions, as new evidence accumulates, we will often have to add more and more complexity to our models

Question 5

copernicus

Answer 5

challenged the geocentric model changing astronomical thinking; calculated sizes of planets orbit

Question 6

heliocentric model

Answer 6

simply explained retrograde motion

Question 7

opposition

Answer 7

when a planet is directly opposite the sun in the sky

Question 8

conjunction

Answer 8

refer to when a planet lies in the same direction as the sun

Question 9

superior conjunction

Answer 9

conjunction on the far side of the sun

Question 10

inferior conjunction

Answer 10

conjunction between earth and sun

Question 11

Brahe

Answer 11

designed, built and used instruments that permitted the most accurate pretelescopic measurments

Question 12

Kepler

Answer 12

Brahe’s assistant; used data of mars’ orbit to prove mars moved in an ellipse

Question 13

semimajor axis

Answer 13

half of an ellipse’s major axis length

Question 14

Kepler’s 1st law

Answer 14

planets move in an ellipse; sun is at a focus

Question 15

Kepler’s 2nd law

Answer 15

the orbital speed of a planet varies so that a line joining the sun and the planet will sweep over equal areas in equal time intervals

Question 16

Kepler’s 3rd law

Answer 16

p^2=a^3

Question 17

Galileo

Answer 17

discovered sun was unperfect with telescope because of sun spots
Church condemned his ideas

Question 18

Galilean satellites

Answer 18

Jupiters moons

Question 19

Altitude

Answer 19

star’s angle above the horizon

Question 20

azimuth

Answer 20

angle measured east ward from true north to the pint on the horizon below the star

Question 21

synodic period

Answer 21

interval between periods of retrograde motion

Question 22

sundial

Answer 22

any tall pole where you can mark the shadow cast by the top of the pole

Question 23

Newton’s first law

Answer 23

a body in motion stays in motion and a body at rest stays at rest unless acted upon by a force

Question 24

Newton’s 2nd law

Answer 24

F=ma

Question 25

Newton’s 3rd law

Answer 25

when 2 bodies interact they create equal and opposite forces on each other

Question 26

Gravitational force

Answer 26

Fg=GMm/d^2

G=6.67 x 10^-11 Nm^2/kg^2

Question 27

Centripetal Force

Answer 27

gravitational force that keeps planets in orbit

Fc=mv^2/d

Question 28

Circular velocity

Answer 28

Fg=Fc

Vc=the square root of GM/d

Question 29

Escape velocity

Answer 29

velocity needed to escape an orbit

Potential energy=kinetic energy