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