Essential cosmic perspective (chapter 4) quiz Flashcards
what did newton and galileo discover
classical physics.
the very small, massive, and very fast require what in modern physics?
the rest interactions dealing with the very small or the very massive or the very fast requires an understanding of modern physics: quantum mechanics and relativity
the speed is how fast?
the speed is how fast, such as 100 kph meaning you’ll go 100 km in 1 hour if you continue at the speed or 200 km in 2 hours
the velocity is determined how?
the velocity is how fast in what direction, such as 100 kphN the velocity is determined with a speedometer and a compass.
what can acceleration do rather than speed up?
Acceleration is not just speeding up, but any change to your motion which includes slowing down or changing direction
can we think of a car having 3 accelerators?
so one can think of a car having 3 accelerators: gas, brake pedal, and steering wheel
what makes sports cars superior?
sports cars are inferior in their greater ability to accelerate: speed up, brake quickly, and turn on a dime
what does it mean to have an acceleration of 2kph/s means that?
to have an acceleration of 2 kp/h means that you speed up 2 kph every second. Initially you might be going a constant speed of 10 kph but then the next second your going 12 kph then 14 kph. means that you are going 2 seconds fast at every every second
what does an acceleration of -2kph/s mean?
an acceleration of -2kph/s means slowing down 2kph each second . from 10 kph you slow down to 8 kph then 6 kph tc.
what is force?
force is push or pull. force is what causes objects to accelerate, to change their motion.
how do you get a box to accelerate from rest?
to get box to accelerate from rest you push it, the wind deflects it, and the friction slows it down. These are forces.
how do you get the box the accelerate more than you need?
if you want the box to accelerate more than you need to push harder or remove some of the contents,
what is mass? and what when there is more mass during acceleration?
mass is the resistance to acceleration. more mass is harder to accelerate. it the matter in the object.
what is weight?
ATYI, weight is the pull of gravity on the object. This is what the author means by true weight.
what is scale force?
ATYI, scale force is the force of the scale on the object. this what the author means by “apparent weight”
is our mass, weight and scale force the same?
ATYI your mass is the same whether you’re on the ground, in an elevator or on the moon.
your weight is the same whether you’re on the ground or in an elevator, but its 1/6 as much on the moon, the scale force is different as the elevator accelerates.
what are the differences with the elevator
scale
when the elevator is moving at a constant speed or not at all the the scale reads your true (weight) However, when the elevator starts up then the scale reads more than your weight and you feel heavier. when the elevator slows down at the top the the scale reads less than your weight and you feel lighter
what are newtons 3 laws of motion?
newtons 3 laws of motion are 3 simple rules which explain how velocity, acceleration, force, and mass relate
who discovered newtons first law of motion?
Galileo
what is newtons first law of motion?
An object moves at constant velocity if there is no net force acting on it
what are objects at rest? objects in motion?
objects at rest (velocity=0 ) tend to remain at rest but then objects in motion tend to remain in motion with no change in either speed or direction unless some force compels them to accelerate, to change their motion.
what does the net force acting on an object represent?
Combined affect of all the individual forces put together
what is force?
force is a vector, a quantity with both magnitude (how much) and a direction (which way). The direction matters
what is mass?
mass is not a vector. its a scalar. only the magnitude matters. speed is a scalar while velocity is a vector
how do you add vectors?
using pethagoreum rule. the combined rule vector is the diaganol of the pathorgoreum
why don’t the glasses fall over during the tablecloth trick?
because they don’t have a sideways force pushing them over.
what happens when the the acceleration is in the same direction, opposite direction, as to motion?
In the same direction/is in the opposite direction /perpendicular, as to motion (velocity) the the car speeds up /slow down/ changes direction
what can you and cant do with direction?
you can both speed up and and change direction, but you can’t speed up and slow down at the same time
what happens when you get rearended in car crash?
I know this) you feel whiplash when you’re rear ended because your head stays in plays until your neck forces it to accelerate.
what happens when acceleration is opposite to the direction you feel thrown in the car?
The acceleration is opposite to the direction you feel thrown in the car. When you speed up/slow down/turn left/ you feel thrown Back/forward/to the right
ATYI what is newtons first law of motion?
: F_net m*a or net force =mass x acceleration
why does it require more force to accelerate a shot put than a baseball?
because the shot put has more mass.
Is the acceleration of the object is always in the same direction as the net force of the object?
yes ATYI
why does the a baseball swinging by a string around your head changes direction because?
because the force of the string pulling it in. without that force, the ball should travel in as straight line
is the force required to accelerate a box full books the same on the earth moon or space?
yes the force required to accelerate a box full of books is the same whether it is on earth, moon, and space, however its easier to lift things on the moon
what is newtons third law of motion?
for any force, there is always an equal and opposite reaction force
what happens when whatever is pushed?
it pushes back ATYI
give an example of acceleration with less mass?
ATYI, jack pushes jill on ice then jill pushes back just as hard. Both accelerate but jill more if she has less mass
atyi why do you accelerate more when you push a wall with exactly the same magnitude force?
because you have less mass, in other words when you push a wall you will go back because you have less weight, the wall is stronger than you are
what happens when you push a car?
it pushes back just as hard as you push and accelerates more because you have more friction. the other day i pushed a car on the side of the ride
what is a true statement about jumping and walking?
to jump you push down on the ground so it pushes you up to walk forward you push back on the ground so it pushes you forward.
what are true statements about weight and reaction force?
weight is the pull down of the earth on you so reaction force is pulling you up on the earth
what are true statements about pulling up on the earth and and accelerating more than earth?
you pull up on the earth just as hard as the earth pulls down. you eccelerate more than the earth because you have less mass
what is linear momentum?
p=mxv its larger if mass or Volume
can a car have the same momentum as a truck?
yes a car can a have the same momentum as a truck if the car is moving fast enough
what is the example of big bob and fast freddy?
if big bob has twice the mass as fast freddy but half the speed then they have the same momentum and should stop dead in their tracks if they collide head on atyi
what does net force do?
net force causes the object to change its momentum. usually the mass is constant so a change in momentum is just a change in velocity, an ecceleration. rockets lose mass
what happens when there is no net force?
then the object doesn’t accelerate or change its linear momentum since the velocity is constant
what happens when there is net force?
there is a change in momentum of one object is exactly equal and opposite to the P of the other object
what does it mean to say linear momentum in conserved?
to say linear momentum is conserved means the total amount of linear momentum before and after is unchanged. linear momentum is conserved if there is no net external force.
what happens when the cue ball is stopped?
when the cue ball is stopped and gives its momentum to the 8-ball then the P of the cue ball is the same size as the volocity in the 8-ball.
what happens when you jump?
the volume of you is the same as for the earth but since the mass of the earth is so much larger the change in velocity if earth is significant
what is angular momentum?
l=m x vx r the angular momentum is the larger the greater mass or the speed or greater size of the curve
what happens when there is no net torque on the circular moving object?
then its angular momentum is convserved
what happens when an ice skater brings in her arms and legs?
then her speed of rotation increases because the radius if her mass decreases but her angular momentum remains constant.
what happens when a slow moving gas cloud contracts due to gravity?
then it necessarily spins faster due to conservation of angular motion.
ddd
dd
dd
dd
what is another quantity that is conserved that we might think cause damage is
energy
what are the two kinds of energy?
kinetic energy which is energy of motion and potential energy which is energy of position. Radiant energy is a kind of kinetic energy
what is the equation for A objects other than light?
KE=1/2 M . V2
why does big bob have less Kentetic energy?
because v2
what is the eqaution for gravitational potential energy?
GPE=mGH
what info for gpe?
When you a raise a ball tan you give it GPE. When it falls then its GPE decreases and becomes more and more KE until it hits the ground when the KE goes into thermal energy which is a kind of microscopic KE
What happens when the planet orbits the sun?
As a planet orbits the sun its GPE and KE change in opposite directions, but the total energy remains unchanged.
what do gasoline and food energy contain?
Gasoline contains chemical potential energy that can be converted into the Kenetic energy of the moving car. Food energy is a kind of chemical potential energy
what happens when an interstellar cloud collapeses?
then the GPE gradually becomes thermal energy, the cloud increases the temperature
what is temperature?
is measure of average microscopic kinetic energy
At the same the temp, what happens to the lighter and heavier molecules?
The lighter oxygen molecules in the room are moving faster on average than the heavier carbon dioxide molecules
what are the 3 common temperature scales and there temperatures?
water freezes at 273 k , 0 deg, celecius, 32 F, water boils at 373k , 100 c 212 F
What burns faster with an oven?
the hot air and the metal inside the oven might be at the same temperature, you burn faster from touching the metal because it has more particles to deliver to your hand.
ATYI
Although space is at high temp since what few particles are there have high average KE, there are so few particles to replace the heat you automatically radiate the way that you would freeze in hot space unless you were in the sunshine
what can you do E=mc2 ?
you can convert a little bit of mass into a lot of energy. Rest. mass -energy is a kind of PE
What was newton genius for?
realizing apples fall for the same reason that the moon falls around the earth. theres no need to invoke some fifth element to explain celestial motion
what happens to falling objects?
it accelerates 10/m/s/s. Initially at rest after 1 sec its falling at 10/m/s then 20m/s if no air friction
what happens when you throw something up?
it slows down 10/m/s/s if initially its going 30 m/s up after 1 sec it will be going 20 m/s then 10 m/s the next second etc.
what happens when you throw something sideways?
this its sideways velocity doesn’t change if there is no air friction) while its downward velocity increases by 10m/s each second
is the ecceleration the same if its downwards, down, or sideways?
the acceleration is the same 10 m/s downwards regardless whether you throw a ball up , down or sideways
true
if you throw something sideways and it falls. if you fired a cannon from a tall mountain fast enough and you could ignore air friction then it could orbit the earth
paper falls fast when crumpled because?
there is less air friction
what happens when there is no air fraction
rocks and feathers fall the same
what happens when there is no air?
then big things fall the same as small things because big things are just lots of small things holding hands.
what was recorded from newtons 2nd law applied to an apple?
f=ma=mg since the acceleration g is the same for all apples, the more the apple’s mass the more the gravitational force
what was recorded about newtons 3rd law?
the apple pulls back on the earth just as hard as the earth pulls on the apple, so the force of gravity also depends on on the mass of the earth
what should gravity do?
diminish with distance otherwise the more massive sun would pull us off the earth.
What did kepler not understand and figure out?
He didnt know the gravity was the cause of celestial orbits, he figured whatever influence of the sun was the cause it should decrease with dist,, squared like paint has to spread out over surface areas of balls by the distance squared
what did newton detirmine?
newton detirmined the acceleration of the moon is 1/3600 of the acceleration of an apple at the earths surface
what is newtons universal law of gravity?
F_G=(GmM)/d2
What didnt newton not know?
He didnt know the value of G. cavendish later detirmined G and mass of the earth using a torsion balance to measure the tiny gravitational force between heavy spheres as they twist a suspension wire
what does the mass of the earth come out to be?
6E24 KG
what is slightly bigger with gravity?
Gravity is slightly bigger at the poles than at the equator since the earth bulges at the equator
when does gravity decrease? g
gravity decreases at the depth becoming zero at the center of the earth since as you go deeper and deeper than there is more and more mass above you pulling you up
what can we know about astronoaughts?
they feel weightless, however astro, have weight thats why they orbit. more precisely ther’re in free fall since they are free of all other forces but gravity
skydivers are in freefall how do they feel?
weightless
what happens when a diver falls?
then air friction gets larger and larger so the net force gets smaller and smaller until the net force is zero, the diver stops accelerating and falls at terminal speed.
what consists of ellipse and circles
ellipses and circles are two kinds of trajectory due to gravity., others are straight lines, parabolas, and hyperbole’s
what do masses orbit?
their common center of mass.
what is newtons version of keplers 3rd law
p2=a3(4pie2/{G(M+m)]}
what does newtons version of keplers third law allow?
the determination of the masses of planets and stars by measuring the orbital period and distances of lower mass objects orbiting them.
for a gravity assist ti add energy relative the sun then the spacecraft do what?
pass behind the planet slowing the planet down
what tidal affect in?
the fact that the near side of a large body is pulled with greater force than the far side causing two tidal bulges to appear, stretching in opposite directions.
what to the moon and the sun produce?
tidal affects on the earth
true statment
although the force of the sun is greater on the earth that the force of the moon on the earth (the earth orbits the sun) the tidal affect of the sun is weaker because the near side of earth isnt that much closer to the sun than the far side % was
when do extra high tides known as spring tides accur?
Extra high tides called spring tides occur when the sun, moon and earth are in line so their affects combine. the weakest tides called neap tides occur at quarter phases when they cancel
what happens when the earth turns under the bulges?
it causes the earth to slow down lenghtening the day 1 second every 50,000 years
true statement
the spin angular momentum that the earth loses goes to increase the orbital momentum of the moon. the moon is receding from the earth about 4 cm every year
