## Physics Principles and Problems-Chapters 1-3

physics

a branch of science that involves the study of the physical world: energy, matter, and how they are related

dimensional analysis

treating units as algebraic quantities, which can be cancelled

significant digits

the valid digits in a measurement

scientific method

making observations, doing experiments, and creating models or theories to try to explain your results or predict new answers

hypothesis

an educated guess about how variables are related

scientific law

a rule of nature that sums up related observations to describe a pattern in nature

scientific theory

an explanation based on many observations supported by experimental results

measurement

a comparison between an unknown quantity and a standard

precision

the degree of exactness of a measurement

accuracy

this describes how well the results of a measurement agree with the “real” value, that is, the accepted value as measured by competent experimenters

independent variable

the factor that is changed or manipulated during an experiment

dependent variable

the factor that depends on the independent variable

line of best fit

a line drawn as close to all data points as possible that is a better model for predictions

linear relationship

when the line of best fit is a straight line. (y = mx + b)

quadratic relationship

this exists when one variable depends on the square of another (y = ax^2 + bx + cx)

inverse relationship

this is when one variable depends on the inverse of another (y = a/x)

motion diagram

a series of images showing the positions of a moving object at equal time intervals

particle model

a simplified version of a motion diagram in which the object in motion is replaced by a series of single points

coordinate system

this tells you the location of the zero point you are studying and the direction in which the values of the variables increase

origin

the point at which both variables have the value zero

position

the separation between an object and the origin

distance

how far away an object is from the origin

magnitude

the size of something

vector

a quantity that has both magnitude and direction

scalar

a quantity without any direction

resultant

a vector that represents the sum of two other vectors

time interval

the difference between two times

displacement

the change in position in an interval of time

position-time graph

a graph in which the time data is on the horizontal (x) axis, and the position data is on the vertical (y) axis

instantaneous position

the position of something at a particular instant

average velocity

the change in position, divided by the time during which the change occurred (the slope of a position-time graph)

average speed

how fast an object is moving (the absolute value of the slope of a position-time graph)

instantaneous velocity

the speed and direction of an object at a particular instant

velocity-time graph

graph in which the time data is on the horizontal (x) axis, and the velocity data is on the vertical (y) axis

acceleration

the rate at which an object’s velocity changes

average acceleration

the change in velocity during some measurable time interval divided by that time interval

instantaneous acceleration

the change in velocity at an instant of time

free fall

the motion of a body when air resistance is negligible and the action can be considered due to gravity alone

acceleration due to gravity

the acceleration of an object in free fall that results from the influence of Earth’s gravity

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