Chapter 1 Motion

Describing and Measuring Motion Motion: the state in which an object’s distance from another object changes. -Whether or not an object is moving depends on the person’s point of view. Reference Point: a place or an object used for comparison to determine if something is in motion.

An object is in motion if it changes positions relative to a reference point.

Are the bike riders moving in relation to one another? NO! because their distance from one another is not changing

Describing Distance Distance: how far an object has traveled measured in length Displacement- distance and direction of an object’s change in position from starting point

Calculating Speed Speed: the distance the object travels in one unit of time. A type of rate: tells you the amount of something that occurs or changes in one unit of time. Average Speed = Distance = m Time s

Type of Speed Description Example Instantaneous Speed at any given point in time Driving a car and looking down to read the speedometer Average Total distance traveled divided by the total time Taking a road trip Constant Speed that does not vary putting car in cruise control

Velocity When you know both the speed and direction of an object’s motion, you know the velocity. Velocity: speed in a given direction

Graphing Motion Distance (m) Time (min) Time is plotted on the horizontal axis and distance is plotted on the vertical axis. A steeper line indicates a greater speed

Graphing Motion Slope: the steepness of the line on a graph Tells you how fast one variable changes in relation to the other variable Represents the rate of change of distance in relation to time Slope = rise = distance run time The steeper the slope, the greater the speed. When slope equals zero, the line is horizontal and the object is NOT MOVING!!

Graphing Motion Distance (m) Time (min) Slope is steeper = Object is moving faster Slope is not as steep = object is moving slower. Distance (m) Time (min)

Graphing Motion Distance (m) Time (min) Object is NOT IN MOTION when the line is horizontal Distance (m) Time (min)

Acceleration the rate at which velocity changes.

Calculating Acceleration Acceleration (m/s2) = Change in Velocity Time  Note** Change in velocity = final velocity-initial velocity   Change in v = vf - vi    Formula for Acceleration Acceleration = vf - vi = m/s2 t

Graphing Acceleration Linear relationship: the graphed line rises the same amount each second.  Nonlinear relationship: the graph of distance versus time is a curved line. The distance traveled by the accelerating object varies each second.