Lesson 4

Question 1

Speed

Answer 1

how fast something will go in a certain amount of time

Question 2

Velocity

Answer 2

tells us speed and direction

Question 3

Acceleration

Answer 3

velocity change in either speed or direction

Question 4

Acceleration of Gravity

Answer 4

g = 9.8 m/s^2

Question 5

Momentum

Answer 5

product of mass times velocity

Question 6

Force

Answer 6

changes an objects momentum

Question 7

Net Force

Answer 7

combined effect of all individual forces put together

• constant velocity = 0 net force
• change in momentum only occurs when net force is not 0
• net force that isn’t 0 causes an object to accelerate

Question 8

Angular momentum

Answer 8

• turning momentum

- ice skater spinning in place

Question 9

Rotational momentum

Answer 9

• Earth’s angular momentum due to it’s rotation and orbit

Question 10

Torque

Answer 10

• type of force that changes angular momentum

- twisting force

Question 11

Mass

Answer 11

amount of matter in body

Question 12

Weight

Answer 12

force that a scale measures when you stand on it (mass and forces)

Question 13

Free-fall

Answer 13

falling without any resistance to slow you down

you become weightless

Question 14

Constant state of free fall example

Answer 14

astronauts orbiting Earth

Question 15

Newton’s first law

Answer 15

an object moves at constant velocity if there is no force acting upon it
- an object at rest stays at rest and object in motion stays in motion unless a force acts on it

Question 16

Newton’s second law

Answer 16

F = ma 
Force = mass x acceleration 
Force = rate of change in momentum

Question 17

Newton’s third law

Answer 17

for any force there is an equal and opposite reaction force

Question 18

Law of conservation of momentum

Answer 18

• as long as there are no external forces, total momentum of interacting objects cannot change

Question 19

Conservation of angular momentum

Answer 19

as long as there is no external torque, total angular momentum of a set of interacting objects cannot change (this is why Earth keeps rotating and orbiting)

Question 20

Orbital angular momentum

Answer 20

angular momentum = m x v x r

• when radius is smaller, velocity must increase to maintain momentum; hence Kepler’s 2nd law

Question 21

Why is Earth gradually slowing down?

Answer 21

it is transferring some of its rotational angular momentum to the Moon

Question 22

Law of conservation of energy

Answer 22

energy can’t be created or destroyed

Question 23

Kinetic energy

Answer 23

energy of motion

- kinetic energy of moving objects = 1/2 mv^2

Question 24

Radiative energy

Answer 24

energy carried by light

Question 25

Potential energy

Answer 25

stored energy, can later be converted to kinetic or radiative energy (ex: gravitational potential energy for a rock balancing on a ledge OR chemical potential energy of gasoline in car)

Question 26

Standard unit of energy

Answer 26

1 C = 4184 joules

Question 27

Thermal energy

Answer 27

- subcategory of kinetic energy - total kinetic energy of all the randomly moving particles in a substance - temperature = average kinetic energy of the particles

Question 28

Potential energy: Gravitational and Mass-energy

Answer 28

- Gravitational potential energy depends on mass and how far it can fall as result of gravity - Mass-energy = amount of potential energy contained in mass ( E =mc^2)

Question 29

Universal law of gravitation

Answer 29

- every mass attracts every other mass through gravity - strength of gravitational force is directly proportional to product of their masses - strength of gravity between two objects decreases with the square of the distance between their centres (inverse square law)

Question 30

Bound vs. unbound orbits

Answer 30

- bound orbits, HAVE to be elliptical; and go around and around - unbound orbits; parabolic/hyperbolic

Question 31

Common centre of mass

Answer 31

point at which two objects would balance if they were connect - when one object is more massive, the centre of mass lies closer to the more massive object

Question 32

Orbital energy

Answer 32

- sum of kinetic and gravitational potential energies

Question 33

Gravitational encounter

Answer 33

two objects pass near enough that each can feel the other's gravity

Question 34

Atmospheric drag

Answer 34

friction causes objects to lose orbital energy

Question 35

Escape velocity

Answer 35

energy needed to escape an orbit | - Earths escape velocity is 11km/s

Question 36

Tidal force

Answer 36

- stretches earth to create two tidal bulges, one toward moon and one away

Question 37

New moon and full moon tide

Answer 37

spring tides; highest tides

Question 38

First and third quarter moon tide

Answer 38

neap tides; lowest tides

Question 39

Tidal friction

Answer 39

Moon's gravity tries to keep tidal bulges on Eath-moon line, and Earth's rotation tires to pull bulges around with it - Slows Earth rotation - Moon moving farther from Earth