Chapter 3

Question 1

Renaissance

Answer 1

A cultural movement spanning the 14th to 17th centuries that encompassed a flowering of education and art, much of which was based on principles established by the ancient greeks

Question 2

Nicolaus Copernicus

Answer 2

developed a heliocentric model for the motions of the sun and planets in the solar system

Question 3

Tycho Brahe

Answer 3

established the basis for a true understanding of planetary motion with naked-eye observations

Question 4

Johannes Kepler

Answer 4

used Tycho’s meticulous observations of planet positions to develop his 3 laws of planetary motion

Question 5

focus (foci)

Answer 5

either of two points interior to an ellipse that are used to define its shape. the sun is always at one focus of a planet’s elliptical orbit

Question 6

first law of planetary motion

Answer 6

the principle by Johannes Kepler stating that planets move on elliptical orbits with the sun at one focus

Question 7

semimajor axis

Answer 7

half of the long axis of an ellipse

Question 8

semiminor axis

Answer 8

half of the short axis of an ellipse

Question 9

eccentricity

Answer 9

a measure of the roundness of an ellipse, calculated as the ratio of the distance from the Earth’s center to its foci, divided by the length of the semimajor axis

Question 10

perihelion

Answer 10

point closest to sun in a planets orbit

Question 11

aphelion

Answer 11

point furthest from the sun in a planets orbit

Question 12

second law of planetary motion

Answer 12

the Kepler principle stating that the line connecting a planet to the sun will sweep out equal areas of its orbit in equal times

Question 13

conservation of angular momentum

Answer 13

the principle whereby a spinning or orbiting object increases its rotational speed as the radius (of either the spinning object or the object’s orbit) decreases, and vice versa

Question 14

orbital period

Answer 14

the time an object takes to complete one revolution of an orbit

Question 15

third law of planetary motion

Answer 15

the principle by Kepler stating that the square of a planet’s orbital period equals its average orbital radius cubed
P^2=R^3

Question 16

Galileo Galilei

Answer 16

played an essential role in establishing the modern practices of sciences such as observation and experimentation. made discoveries with low-power telescopes that revolutionized astronomy.

Question 17

Galilean moons

Answer 17

the four largest moons of Jupiter: Io, Ganymede, Callisto, and Europa

Question 18

Sunspots

Answer 18

dark spots on the sun

Question 19

nebulosity

Answer 19

a word used by astronomers for clouds in space

Question 20

force

Answer 20

an interaction between two bodies that, if unbalanced, can change their state of motion

Question 21

mass

Answer 21

a property of matter that is related to its resistance to changes in motion or inertia. mass is measured in units of kilograms

Question 22

velocity

Answer 22

the change of a distance and the direction in which it is changing per unit of time

Question 23

speed

Answer 23

the change in distance per unit of time

Question 24

acceleration

Answer 24

the change of velocity per unit time

Question 25

inertial law

Answer 25

principle advanced by isaac newton stating that objects in motion at constant velocity along a straight line continue that ay unless acted on by a net force

Question 26

force law

Answer 26

principle advanced by isaac newton stating that the change in an object's acceleration due to an applied net force is in the same direction as the force and directly proportional to the object's mass

Question 27

reaction law

Answer 27

the principle by isaac newton stating that for every applied force there is an equal and opposite force

Question 28

momentum

Answer 28

the tendency of a moving object to continue in motion. only the application of a force can change an object's momentum

Question 29

gravity

Answer 29

an attractive force between any two massive bodies that depends on the product of the bodies' masses and the inverse square of the distance between them

Question 30

constant of nature

Answer 30

a term that does not change from one situation or time to another. the value of a constant of nature must be measured to be determined.

Question 31

inverse square law

Answer 31

a relationship whereby a quantity (such as gravity) decreases in proportion to the square of a variable (such as distance) as the latter increases

Question 32

weight

Answer 32

the force of an object that is produced by gravity

Question 33

centripetal acceleration

Answer 33

acceleration involving a force that keeps an object moving on a curved path. the acceleration is directed toward the center of curvature of the path

Question 34

centrifugal force

Answer 34

the illusion of outward force when an object is moving on a curved path

Question 35

orbital velocity

Answer 35

the velocity required to keep a body in orbit around another body

Question 36

escape velocity

Answer 36

the velocity required to escape the pull of gravity from a body