Chapter 4

Question 1

Law of conservation of angular momentum

Answer 1

the principle that, in the absence of net torque, the total angular momentum of a system remains constant

Question 2

Unbound orbits

Answer 2

orbits on which an object comes in toward a large body only once, never to return

Question 3

Gravitational constant

Answer 3

the experimentally measured constant G that appears in the law of universal graviation

Question 4

Radiative energy

Answer 4

energy carried by light

Question 5

Kelvin

Answer 5

the temperature scale most commonly used in science

Question 6

Kinetic energy

Answer 6

energy of motion

Question 7

Tidal force

Answer 7

a force that occurs when the gravity pulling on one side of an object is larger than that on the other side, causing the object to stretch

Question 8

Momentum

Answer 8

the product of an object’s mass and velocity

Question 9

Net force

Answer 9

the overall force to which an object responds

Question 10

Free-fall

Answer 10

the condition in which an object is falling without resistance

Question 11

Thermal energy

Answer 11

the collective kinetic energy, as measured by temperature, of the many individual particles moving within a substance

Question 12

Temperature

Answer 12

a measure of the average kinetic energy of particles in a substance

Question 13

Escape velocity

Answer 13

the speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star

Question 14

Acceleration

Answer 14

the rate at which an object’s velocity changes

Question 15

Bound orbits

Answer 15

Orbits on which an object travels repeatedly around another object

Question 16

Angular momentum

Answer 16

momentum attributable to rotation or revolution

Question 17

Speed

Answer 17

the rate at which an object moves

Question 18

Mass

Answer 18

a measure of the amount of matter in an object

Question 19

Acceleration of gravity

Answer 19

the acceleration of a falling object

Question 20

Orbital energy

Answer 20

the sum of an orbiting object’s kinetic and gravitational potential energies

Question 21

Newton’s version of Kepler’s third law

Answer 21

a generalization of Kepler’s third law used to calculate the masses of orbiting objects from measurements of orbital period and distance

Question 22

Mass-energy

Answer 22

the potential energy of mass, which has an amount E=mc^2

Question 23

Gravitational encounter

Answer 23

an encounter in which two objects pass near enough so that each can feel the effects of the other’s gravity and they can therefore exchange energy

Question 24

Weight

Answer 24

the net force that an object applies to its surroundings

Question 25

Universal law of gravitation

Answer 25

the law expressing the force of gravity (Fg) between two objects

Question 26

Inverse square law

Answer 26

a law followed by any quantity that decreases with the square of the distance between two objects

Question 27

Joule

Answer 27

the international unit of energy, equivalent to about 1/4000 of a Calorie

Question 28

Velocity

Answer 28

the combination of speed and direction of motion

Question 29

Gravitational potential energy

Answer 29

energy that an object has by virtue of its position in a gravitational field

Question 30

Weightless

Answer 30

a weight of zero

Question 31

Newton's laws of motion

Answer 31

three basic laws that describe how objects respond to forces

Question 32

Potential energy

Answer 32

energy stored for later conversion into kinetic energy

Question 33

Force

Answer 33

anything that can cause a change in momentum

Question 34

Law of conservation of energy

Answer 34

the principle that energy can be neither created nor destroyed, but can only change from one form to another