Cosmic Perspective Chapter 4 Terms

Front 1

speed

Back 1

the rate at which an object moves

Front 2

velocity

Back 2

the combination of speed and direction of motion

Front 3

acceleration

Back 3

the rate at which an object's velocity changes

Front 4

acceleration of gravity

Back 4

the acceleration of a falling object

Front 5

momentum

Back 5

the product of an object's mass and velocity

Front 6

force

Back 6

anything that can cause a change in momentum

Front 7

net force

Back 7

the overall force to which an object responds; rate of change in the object's momentum; object's mass times acceleration

Front 8

angular momentum

Back 8

momentum attributable to rotation or revolution; m x v x r (mass, velocity, radius)

Front 9

torque

Back 9

a twisting force that can cause a change in an object's angular momentum

Front 10

mass

Back 10

a measure of the amount of matter in an object

Front 11

weight

Back 11

the net force that an object applies to its surroundings; weight = mass x acceleration of gravity

Front 12

free-fall

Back 12

conditions in which an object is falling without resistance; objects are weightless in free-fall

Front 13

weightless

Back 13

a weight of zero (occurs during free-fall)

Front 14

Newton's first law of motion

Back 14

in the absence of a net force, an object moves with constant velocity

Front 15

Newton's second law of motion

Back 15

how a net force affects an object's motion; force = mass x acceleration

Front 16

Newton's third law of motion

Back 16

for any force, there is always an equal and opposite reaction force

Front 17

conservation of momentum

Back 17

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

Front 18

conservation of angular momentum

Back 18

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

Front 19

conservation of energy

Back 19

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

Front 20

kinetic energy

Back 20

energy of motion; .5mv^2

Front 21

radiative energy

Back 21

energy carried by light; Planck's constant x frequency

Front 22

potential energy

Back 22

energy stored for later conversion into kinetic energy

Front 23

thermal energy

Back 23

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

Front 24

temperature

Back 24

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

Front 25

Kelvin

Back 25

the most commonly used temperature scale in science, absolute zero = 0 and water freezes at 273.15

Front 26

gravitational potential energy

Back 26

energy that an object has by virtue of its position in a gravitational field (an object has more when it has a greater distance to fall)

Front 27

mass-energy

Back 27

the potential energy of mass

Front 28

universal law of gravitation

Back 28

the law expressing the force of gravity between two objects

Front 29

inverse square law

Back 29

any quantity that decreases with the square of the distance between two objects

Front 30

gravitational constant

Back 30

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

Front 31

bound orbits

Back 31

orbits on which an object travels repeatedly around another objects; elliptical in shape

Front 32

unbound orbits

Back 32

orbits on which an object comes in toward a large body only once, never to return; parabolic or hyperbolic in shape

Front 33

center of mass

Back 33

the point at which two or more orbiting objects would balance if they were somehow connected; the point around which orbiting objects actually orbit

Front 34

Newton's version of Kepler's third law

Back 34

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

Front 35

orbital energy

Back 35

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

Front 36

gravitational encounter

Back 36

occurs when two or more objects pass near enough so that each can feel the effects of the other's gravity and can therefore exchange energy

Front 37

tidal force

Back 37

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

Front 38

tidal friction

Back 38

friction within an object that is caused by a tidal force

Front 39

synchronous rotation

Back 39

the rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are equal

Front 40

escape velocity

Back 40

the speed necessary for an object to completely escape the gravity of a large body

Front 41

joule

Back 41

the international unit of energy which is about 1/4000 of a calorie