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# HELUS8CH1

### 8th grade physical science: chapter 1: Motion

A ___ is a starting point used to describe the position of an object. reference point
The ___ is the direction you must travel from the reference point toward an object. reference direction
Units like ___ (m), kilometers (km), and centimeters (cm) are used to describe distances. meters
To describe an object’s position, you must include three pieces of information: a reference point, a reference direction, and the distance from the reference point in the ___. reference direction
Positive (+)and ___ (-) measurements of distance are often used to describe positions negative
___ measurements are usually in the reference direction, or toward the object from the reference point. Positive
Negative measurements are usually in the opposite direction from the reference direction.Negative measurements are usually in the ___ direction from the reference direction.They start from the reference point and measure away from the object opposite
One way to describe the position of an object is as an ___ pointing from a reference point toward the object arrow
A ___ is a quantity that has both a size and a direction vector
Vectors are often drawn as ___ pointing away from a reference point in the referencedirection. arrows
___ is one example of a vector. Position
The length of a position vector is the ___ from the reference point to the object whose position the vector represents distance
Maps have two ___, east-west and north-south. reference directions
A two-dimensional map can be drawn as a graph used to represent the location of objects with two ___ reference directions
East is usually on the positive ___, and north is usually on the positive ___. x-axis. y-axis
A location must be chosen to be the reference point, or ___, of the graph. origin
___ is the difference between the initial position and the final position of an object. Displacement
Displacement is measured as a distance from a reference point in a particular direction, and so displacement is a ___. vector
A ___ measures the change in one quantity in a particular length of time rate
___ is the rate of change of position over a period of time Speed
An object that moves at a ____ travels the same distance each and every second constant speed
___, or the speed of an object at a specific instant of time, is especially useful to measure for objects whose speed changes. Instantaneous speed
An object’s ___ is its total distance traveled divided by the total time it traveled average speed
The equation for average speed is average speed = total distance divided by ____. total time
If you know any two quantities in the average speed equation, you can use the equation to calculate the ___. third
The unit for speed is a ___ unit divided by a time unit. The SI unit for speed is ___ distance, m/s
___ is a measurement of both the speed and direction of motion of an object Velocity
Velocity is a ___. It has both a size (the speed of the object) and a direction (the direction the object is moving) vector
Speed is different from ___ because speed does not include the direction in which the object is moving velocity
___, another vector, is the rate at which velocity changes over time Acceleration
When an object speeds up, the direction of its ___ is the same as the direction of its motion. acceleration
When an object ___, its acceleration is in the opposite direction from the direction of its motion slows down
When an object changes the direction in which it is moving, its velocity changes. This means that it is ___ accelerating
On a position-time graph, ___ is usually plotted on the y-axis and time is usually plotted on the ___. position, x-axis
The ___ of a line is the steepness of the line. slope
On a position-time graph, an object’s speed can be determined by looking at the ___ of the line that represents that object’s motion. slope
On a position-time graph, the steeper the slope of a line, the ___ the object was moving. faster
On a position-time graph, the flatter the slope of the line, the ___ the object was moving slower
The vertical change, or change along the y-axis, on a graph as an object moves between two points is sometimes called the ___. rise
The horizontal change, or change along the x-axis, on a graph as an object moves betweentwo points is sometimes called the ___ run
The ___ of a line can be calculated by dividing the rise between two points on the line by the run between the same two points slope
Only objects moving at ___ speeds have straight line position-time graphs constant
The average speed of the entire trip of an object that does not move at constant speed can be calculated by finding the slope between the ___ and ___ data points on the graph of the object’s motion. starting, ending
If a ___ graph has a horizontal line, the object whose speed the graph represents was moving at a constant speed. speed-time
If an object speeds up, its line on a speed-time graph curves up to the right. The steeper the slope, the faster its speed is ___. increasing
When an object ___, its line on a speed-time graph slopes down to the right slows down
Created by: jnosik