Units 1-2 Flashcards
True or False: Incline is a factor of acceleration
False
What are the four ways we gain knowledge?
Authority, Intuition, Reason, Sensory Data
Authority
An accepted source of information or advice. You trust them to know best on the issue.
Intuition
The act of knowing or sensing without the use of rational processes. Something like a “hunch” or a “feeling.” Revelation would be included her, as well as immediate cognition.
Reason
Logical, rational, analytic thought - basic intelligence
Sensory Data
Knowledge obtained through the senses.
Why is authority knowledge important?
Because we physically can’t experience everything ourselves. We have to rely on the experiences of others.
What concepts are involved with the scientific method?
Hypotheses, theory, laws, and models
How many truths are “self evident”?
6
What does “self evident” truth mean?
These are the assumptions of the whole scientific community about the natural world. They are incredibly logical theories that are accepted as “truth.”
List the six self evident truths:
- Existence
- Causality
- Position symmetry
- Time symmetry
- Non-Contradiction
- Occam’s razor
What is the existence assumption?
There exists a physical world separate and distinct from our minds that is comprehensible through our senses. This world is governed by the “laws of nature.”
What is the causality assumption?
Cause must always precede the effect.
Events in the physical world have natural causes that can be explained in terms of the laws of nature.
What is the position symmetry assumption?
That the laws of nature will act exactly the same anywhere in the universe.
What is the time symmetry assumption?
That the laws of nature have remained the same through time and will not change.
What is the non-contradiction assumption?
If there are two contradictory propositions, at least one of them must be false.
Both cannot be true. It’s possible neither of them are true.
What is the Occam’s razor assumption?
If there are alternative explanations of any phenomenon, that are all logical and explain the phenomenon equally well, the simplest explanation will be chosen.
Simple is better.
How many interactive forces do we know of in the universe?
Four
What are the interactive forces we know of?
- Strong force (or nuclear strong force)
- Electromagnetic force
- Weak force (or nuclear weak force)
- Gravity
What is a force?
A push or a pull.
What is the strongest force we know of?
Nuclear strong force
What is the weakest force we know of?
Gravity
When is the strong force strong?
When it is interacting with things smaller than the size of an atom.
What is the strongest force at atom level?
Electromagnetic
Which force dominates the world that we live in?
Electromagnetic
At what scale does gravity dominate?
Planets and solar systems (or larger)
What are atomic nuclei composed of?
Nucleons
What are nucleons?
Protons and neutrons
What are protons and neutrons made of?
Quarks
What is an atomic nuclei?
The positively charged central region of an atom.
What is a proton?
A positively charged particle in an atomic nuclei.
Made of 3 quarks.
What is a neutron?
An uncharged particle in an atomic nuclei.
Made of 3 quarks.
What does it mean if an atom is radioactive?
It means the nuclei is susceptible to being changed or broken apart from the weak force.
They can change spontaneously.
How does the electromagnetic force act on atomic nuclei?
It acts as a repulsion between protons (which are all positively charged, think of magnets).
Why do nuclei not explode apart due to the electromagnetic force?
Because the strong nuclear force is still more powerful at that distance, and it holds them together.
What surround atomic nuclei?
Electrons
What is an electron?
A particle in an atom (NOT the nuclei) that has a negative charge.
These are located outside of the nuclei inside an atom.
What is an atom?
The fundamental unit of an element.
What is an element?
A substance composed of the same number of protons in their nuclei.
What is a molecule?
The tiniest particles of a substance that retain all the physical properties of that substance, made up of more than one atom.
What does the left hand number mean on the periodic table?
How many protons the element has.
What force creates molecules from atoms?
Electromagnetic
True or False: In all cases, without exception, if something moved, it or some part of it moved.
True
True or False: Motion is fundamental to all change on earth.
True
True or False: Something at rest will only move if a force is applied to it.
True
True or False: Force is necessary to both create motion and sustain it.
FALSE
Force is not required to sustain motion.
True or False: An object will remain in motion so long as no impeding forces, like friction, act against the motion.
TRUE
Who understood the laws of motion before Newton?
Galileo
What is the first law of motion?
Every object at rest, or in uniform motion, will remain in that state of motion unless acted upon by other forces.
Uniform motion
Motion at a constant speed in a straight line
What is the state of uniform motion?
The condition of an object when no unbalanced forces are acting upon it. It is either at rest or in uniform motion.
What is a force?
A push or a pull on an object.
What two factors contribute to the state of motion?
Speed and direction
True or False: Speed is a unique quantity like size or shape.
FALSE
Speed is relative, it depends on what you are measuring it against.
True or False: The state of rest is just the state of uniform motion with zero speed.
True
What is the state of motion?
Speed + direction
What is another name for speed + direction?
VELOCITY!
What is acceleration?
A change in an object’s velocity.
In other words, acceleration is a change in either speed or direction.
What is centripetal acceleration?
Acceleration toward a center.
Meaning, acceleration happening at a RIGHT ANGLE (perpendicular) to an object’s velocity.
This will change the direction but NOT the speed.
True or False: Acceleration is the RATE by which velocity changes (speed or direction).
True
True or False: Incline is a measurement of direction.
FALSE
What is the net force?
The sum of all the forces acting on an object
Is acceleration a part of uniform motion?
NO!
True or False: Acceleration is caused by force.
TRUE
True or False: If a force is present it causes an acceleration.
False!
This is not ALWAYS true. A force can be present without causing acceleration.
But a force is required to cause acceleration.
What does the net force have to be to stop causing acceleration?
zero
What kind of forces is acceleration caused by?
Unbalanced forces
What are unbalanced forces?
Any time the net force is not zero.
It is the portion of the net force that is unopposed by other forces (pushing or pulling in one direction because that force is greater).
Define mass in terms of this class
It is a characteristic of an object that determines how much the object accelerates when a force is applied.
True or False: The mass determines how much an object accelerates.
True
True or False: An object accelerates or decelerates depending on the direction of the force applied.
TRUE
What is used to measure the strength of a force in the U.S.?
Pounds (lbs)
Newtons in the metric system (N)
What two factors determine the AMOUNT of acceleration/deceleration?
- The strength of the force
- The mass of the object
True or False: The greater the mass the greater the acceleration.
FALSE.
Acceleration is smaller when mass is larger.
True or False: Mass is a unique property of an object.
True
True or False: A particular force applied to a mass causes the same amount of acceleration no matter WHERE the object is located (on earth or in space).
TRUE
Is mass the same thing as weight?
No
What is weight?
Weight is a measure of the force of gravity on a particular mass.
Does mass change with location?
No
Does weight change with location?
Yes (because it is determined by gravity, it is relative).
Weight is relative
What is inertia?
Thought of as the property that makes it hard to move an object from rest, or that keeps it moving once it has started.
I.e. The property that makes it difficult to get an object to change its state of motion.
What is another name for Newton’s 1st law?
The law of inertia
What does mass represent?
Basically inertia. Inertia is a qualitative description of mass.
Mass represents the difficulty of getting an object to change its state of motion.
What is Newton’s 2nd Law of motion?
Force = mass x acceleration
Or just
F = ma
True or False: Acceleration is directly proportional to the force on the object.
True
What is another way to write the 2nd law of motion?
a = F / m
True or False: Acceleration is inversely proportional to the mass of an object.
TRUE
Why is the 2nd law of motion important?
Because it was the first universal principle that enabled us to describe changes in our physical world through mathematics.
What is Newton’s 3rd law of motion?
Forces occur ONLY when TWO THINGS interact with each other.
Nothing in isolation can exert a force on itself.
AKA: Every action produces an equal and opposite reaction (except it’s not a reaction).
True or False: In every interaction, at least two forces arise
True
Where do the opposing forces show up in an interaction?
On BOTH of the interacting objects
True or False: Forces arising from an interaction have the same strength and act (push or pull) in exactly opposite directions.
TRUE
Very key.
True or False: A single sided interaction can exist.
FALSE
True or False: In every interaction there will ALWAYS be two forces, one on each object.
True
What happens when the two interacting objects have the same mass?
The two forces cause both objects to accelerate the same amount.
True or False: A ball being swung around on a string is accelerating.
True
Because it is changing direction, which is a change in velocity, which is acceleration.
What is the change of direction caused by in the example of a ball being swung around on a string?
Centripetal force, caused by the string pulling the ball inwards towards the center.
What happens to the ball when the person lets go of the string?
The centripetal force is no longer acting upon the ball, so it continues to move in the same speed (that it was going at that moment of release) in the same direction until acted upon by another force (wind, friction, gravity, etc.)
True or False: Newton’s 1st law describes the world as if there were no forces at all.
True
At what three times in nature does Newton’s 1st law apply?
- When there are balanced forces.
- When an object is at rest
- When the object is in uniform motion.
True or False: Deceleration is just acceleration but in an opposite direction
True
This class will just use “acceleration” generally and not worry about deceleration.
What is mass measured in?
Grams or kilograms
True or False: The EFFECT of a force depends on the direction of the net force compared to the motion.
True
When is Newton’s 2nd law used?
- Any time there are unbalanced forces (a net force greater than zero)
- Any time the motion of an object is changing (speed, direction, or both)
True or False: In EVERY situation, either the 1st or 2nd law can be applied.
True.
Either an object IS moving (2nd) or it is in uniform motion (1st). Always.
True or False: All forces that are equal and opposite are interaction pairs according to Newton’s 3rd law.
FALSE
Interaction pairs and the forces involved MUST be between a set of objects. The opposing forces must be on a pair of objects that are interacting, not just any forces involved.
True or False: The third law of motion doesn’t have anything to do with motion.
True
True or False: The 3rd law of motion measures net force
FALSE
It measure the strength of a single interaction.
True or False: In an interactive pair, the forces must be the same KIND of force to be “paired.” (ie. gravity against gravity, contact against contact, etc.)
TRUE
