TTU K-12 Physics 1A Midterm

natural philosophy

the study of unanswered questions about nature; now called "science"

physics

the study of the nature of basic things such as motion, forces, energy, heat, sound, light, and the composition of atoms; the most basic of all sciences

scientific method

a method founded by Galileo Galilei and Francis Bacon that is extremely effective in gaining, organizing, and applying new knowledge

steps of the scientific method

1. Recognize a problem
2. Make an educated guess about the answer (hypothesis)
3. Predict the consequences of the hypothesis
4. Perform experiments to test predictions
5. Formulate the simplest general rule that organizes the three main ingredients: hypothesis, prediction, and experimental outcome

fact

a close agreement by competent observers who make a series of observations of the same phenomenon

scientific hypothesis

an educated guess that is only presumed to be factual until supported by experiment

laws/principles

only formed when hypotheses are tested over and over again and not contradicted

theory

a synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world

1 km/1000 m

5285 meters x ________ = 5.285 km

0.892 kg

892 grams = ________ kg

1000 mL/1 L

0.60792 liters x ________ = 607.92 mL

1000 m/1 km

6.2 km x ________ = 6200 m

significant figures

a way of accounting for the known number in a value; these numbers are known with certainty

insignificant/uncertain figures

numbers in a value which are estimated or used as a place holder

rules of significant figures

1. All non-zero numbers are significant (ex. 4.564 - 4 significant digits)
2. All zeros between significant digits are significant (ex. 809 - 3 significant digits)
3. Zeros to the right of the decimal and to the right of a significant digit are significant (ex. 55.300 - 5 significant digits)
4. Zeros to the left of the decimal and to the right of a significant digit are significant (ex. 1500. - 4 significant digits)

rules of insignificant figures

1. Zeros that are used only as place holder and there is no specified decimal point are not significant (ex. 300 - 1 significant digit)
2. Zeros that are to the right of a decimal point but to the left of a non-zero digit are not significant (ex. 0.005 - 1 significant digit)

rate

a quantity divided by time; tells how fast something happens or how much something changes in a certain amount of time

speed

a measure of how fast something is moving; the rate at which distance is covered (distance divided by a unit of time)

instantaneous speed

the speed at any instant

average speed

total distance covered / time interval

velocity

speed in a given direction

acceleration

the rate at which the velocity is changing (with respect to time); change in velocity or speed / time interval

free fall

affected only by gravity; often represented by the letter "g" for gravity

elapsed time

the time that has elapsed since the beginning of the fall

nonlinear motion

motion along a curved path

vector quantity

a quantity that requires both magnitude and direction for a complete description

scalar quantity

a quantity that is completely described by magnitude only; can be added, subtracted, multiplied, and divided like ordinary numbers

vector

an arrow used to represent the magnitude and direction of a vector quantity; length indicates magnitude while direction indicates direction

resultant

the result of adding two vectors; sum without numbers

length of a diagonal for any square

√2 = ~1.414 times either of the sides

component vectors

two vectors at right angles to each other which replace a single vector

resolution

the process of determining the components of a vector

relationship between horizontal force and velocity

when no horizontal force acts on a projectile, the horizontal velocity remains constant; no gravitational force acts horizontally

parabola

the path traced by a projectile accelerating only in the vertical direction while moving at constant horizontal velocity

satellite

a projectile traveling fast enough to fall around Earth rather than into it

projectile

an object with motion only affected by its initial velocity and gravity; always parabolic (neglecting air resistance)

motion is relative

things are moving or at rest based on our frame of reference or relative to other objects

two types of speed

instantaneous and average

horizontal velocity

not affected by gravity; a constant velocity the entire time an object is in the air; velocity = distance/time

vertical velocity

affected by gravity; is not constant; velocity = acceleration x time

horizontal distance

distance = velocity x time

vertical distance

distance = 1/2at²

natural motion

internal cause; motion that is straight up and down in which objects seek their natural resting places (heavy things fall and light things rise)

violent motion

external cause; imposed motion that is the result of forces that push or pull (imparted to objects)

force

any push or pull

friction

the force that acts between materials that touch as they move past each other; caused by the irregularities in the surfaces of objects that are touching

inertia

a material objects resistance of change to its state of motion

Newton's first law

law of inertia; states that every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted upon it; "things tend to keep on doing what they're already doing"

amount of inertia in an object

depends on its mass - which is roughly the amount of material present in the object

mass

a measure of the amount of material (matter) in an object; directly proportional to weight but not volume or weight

weight

a measure of the force of gravity on an object

SI unit of mass

kilogram (kg)

SI unit of force

newton (N)

formula for weight

weight = mass x acceleration due to gravity (weight = mg)

net force

the combination all forces acting on an object; changes an object's state of motion

state of equilibrium

when an object is at rest, with the net force on it being zero

Newton's second law

states that the acceleration produced by a net force on an object is directly proportional to the magnitude of the net force, is in the same direction of the net force, and is inversely proportional to the mass of the object (acceleration = net force/mass)

fluids

liquids and gases

fluid friction

occurs as an object pushes aside the fluid it is moving through

air resistance

type of fluid friction; the friction action on something moving through air

free-body diagram

a diagram showing all the forces acting on an object

pressure

the amount of force per unit of area; perpendicular to surface area

formula for pressure

pressure = force/area of application (P = F/A)

pascals (Pa)

newtons per square mile

terminal speed

when air resistance equals weight and acceleration terminates

Newton's third law

states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object; the action and reaction forces are partners in a single interaction and neither force exists without the other; "to every action there is always an equal and opposite reaction"

lift

upward reaction force

negative velocity toward the car and positive acceleration back to the house

Krista walks at a constant speed to her car and suddenly realizes she forgot her phone. She runs back to the house to get it. Her motion could be described as having

1.2 m

A kitten knocks a toy off a book shelf and it hits the floor in 0.5 s. How high is the shelf from the floor?

time

Which of the following is not a vector quantity?

90 N

The acceleration due to gravity on the moon is 1/6 that on Earth. What would a 55 kg astronaut weigh on the moon?

mass of the ball and net force placed on the ball

What two variables affect the acceleration of a ball?

decrease by a factor of 3

If you put pennies in the back of a toy dump truck so that the total mass (pennies + truck) is three times the mass of the empty truck, and you push it as hard as you did when it was empty, the truck's forward acceleration will

the rope pulling on Judy

Judy plays tug-of-war with Dana. If Judy pulls the rope, the reaction force is

momentum

inertia in motion; the mass of an object multiplied by its velocity

formula for momentum

momentum = mass x velocity (momentum = mv)

impulse

change in momentum; force x time interval

time and force of impact

when you extend the time of impact, you reduce the force of impact

conserved

when momentum, or any quantity of physics, does not change

law of conservation of momentum

in the absence of an external force, the momentum of a system remains unchanged

elastic collision

when objects collide without being permanently deformed and without generating heat

inelastic collision

whenever colliding objects become tangled or couple together

work

force x distance

two categories of work

work done against another force and work done to change the speed of an object

unit of work

newton-meter (N-m) or joule

power

how fast work is done; work done/time interval

watt

unit of power; joule per second

mechanical energy

energy that is stored and held in readiness which has the potential for doing work

gravitational potential energy

potential energy due to elevated positions; weight x height (PE = mgh)

kinetic energy

energy of motion

formula for kinetic energy

kinetic energy = 1/2 mass x speed² (KE = 1/2mv²); kinetic energy = net force x distance (Fd = 1/2mv²)

work-energy theorem

whenever work is done, energy changes

law of conservation of energy

energy cannot be created or destroyed; it can be transformed from one form into another, but the total amount of energy never changes

machine

a device used to multiply forces or simply to change the direction of forces

fulcrum

the pivot point of a lever

mechanical advantage

the ratio of the output force to the input force for a machine

pulley

a kind of lever that can be used to change the direction of a force

formula for efficiency

efficiency = useful work output/total work output; efficiency = actual mechanical advantage/theoretical mechanical advantage; always a fraction less than 1