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PHYS 284 - Astronomy > Lesson 4 > Flashcards

Lesson 4 Flashcards

1
Q

Speed

A

how fast something will go in a certain amount of time

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2
Q

Velocity

A

tells us speed and direction

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3
Q

Acceleration

A

velocity change in either speed or direction

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4
Q

Acceleration of Gravity

A

g = 9.8 m/s^2

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5
Q

Momentum

A

product of mass times velocity

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6
Q

Force

A

changes an objects momentum

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7
Q

Net Force

A

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
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8
Q

Angular momentum

A
  • turning momentum

- ice skater spinning in place

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9
Q

Rotational momentum

A
  • Earth’s angular momentum due to it’s rotation and orbit
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10
Q

Torque

A
  • type of force that changes angular momentum

- twisting force

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11
Q

Mass

A

amount of matter in body

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12
Q

Weight

A

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

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13
Q

Free-fall

A

falling without any resistance to slow you down

you become weightless

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14
Q

Constant state of free fall example

A

astronauts orbiting Earth

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15
Q

Newton’s first law

A

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

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16
Q

Newton’s second law

A 
F = ma 
Force = mass x acceleration 
Force = rate of change in momentum
17
Q

Newton’s third law

A

for any force there is an equal and opposite reaction force

18
Q

Law of conservation of momentum

A
  • as long as there are no external forces, total momentum of interacting objects cannot change
19
Q

Conservation of angular momentum

A

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)

20
Q

Orbital angular momentum

A

angular momentum = m x v x r

  • when radius is smaller, velocity must increase to maintain momentum; hence Kepler’s 2nd law
21
Q

Why is Earth gradually slowing down?

A

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

22
Q

Law of conservation of energy

A

energy can’t be created or destroyed

23
Q

Kinetic energy

A

energy of motion

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

24
Q

Radiative energy

A

energy carried by light

25
Q

Potential energy

A

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)

26
Q

Standard unit of energy

A

1 C = 4184 joules

27
Q

Thermal energy

A
  • subcategory of kinetic energy
  • total kinetic energy of all the randomly moving particles in a substance
  • temperature = average kinetic energy of the particles
28
Q

Potential energy: Gravitational and Mass-energy

A
  • 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)
29
Q

Universal law of gravitation

A
  • 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)
30
Q

Bound vs. unbound orbits

A
  • bound orbits, HAVE to be elliptical; and go around and around
  • unbound orbits; parabolic/hyperbolic
31
Q

Common centre of mass

A

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

32
Q

Orbital energy

A
  • sum of kinetic and gravitational potential energies
33
Q

Gravitational encounter

A

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

34
Q

Atmospheric drag

A

friction causes objects to lose orbital energy

35
Q

Escape velocity

A

energy needed to escape an orbit

- Earths escape velocity is 11km/s

36
Q

Tidal force

A
  • stretches earth to create two tidal bulges, one toward moon and one away
37
Q

New moon and full moon tide

A

spring tides; highest tides

38
Q

First and third quarter moon tide

A

neap tides; lowest tides

39
Q

Tidal friction

A

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

PHYS 284 - Astronomy (5 decks)

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