Lesson 4 Flashcards
Speed
how fast something will go in a certain amount of time
Velocity
tells us speed and direction
Acceleration
velocity change in either speed or direction
Acceleration of Gravity
g = 9.8 m/s^2
Momentum
product of mass times velocity
Force
changes an objects momentum
Net Force
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
Angular momentum
- turning momentum
- ice skater spinning in place
Rotational momentum
- Earth’s angular momentum due to it’s rotation and orbit
Torque
- type of force that changes angular momentum
- twisting force
Mass
amount of matter in body
Weight
force that a scale measures when you stand on it (mass and forces)
Free-fall
falling without any resistance to slow you down
you become weightless
Constant state of free fall example
astronauts orbiting Earth
Newton’s first law
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
Newton’s second law
F = ma Force = mass x acceleration Force = rate of change in momentum
Newton’s third law
for any force there is an equal and opposite reaction force
Law of conservation of momentum
- as long as there are no external forces, total momentum of interacting objects cannot change
Conservation of angular momentum
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)
Orbital angular momentum
angular momentum = m x v x r
- when radius is smaller, velocity must increase to maintain momentum; hence Kepler’s 2nd law
Why is Earth gradually slowing down?
it is transferring some of its rotational angular momentum to the Moon
Law of conservation of energy
energy can’t be created or destroyed
Kinetic energy
energy of motion
- kinetic energy of moving objects = 1/2 mv^2
Radiative energy
energy carried by light
Potential energy
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)
Standard unit of energy
1 C = 4184 joules
Thermal energy
- subcategory of kinetic energy
- total kinetic energy of all the randomly moving particles in a substance
- temperature = average kinetic energy of the particles
Potential energy: Gravitational and Mass-energy
- 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)
Universal law of gravitation
- 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)
Bound vs. unbound orbits
- bound orbits, HAVE to be elliptical; and go around and around
- unbound orbits; parabolic/hyperbolic
Common centre of mass
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
Orbital energy
- sum of kinetic and gravitational potential energies
Gravitational encounter
two objects pass near enough that each can feel the other’s gravity
Atmospheric drag
friction causes objects to lose orbital energy
Escape velocity
energy needed to escape an orbit
- Earths escape velocity is 11km/s
Tidal force
- stretches earth to create two tidal bulges, one toward moon and one away
New moon and full moon tide
spring tides; highest tides
First and third quarter moon tide
neap tides; lowest tides
Tidal friction
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
