SPEED, VELOCITY AND ACCELERATION Motion

Distance & Displacement

Frame of Reference Motion: a change in position relative to a frame of reference Frame of Reference: The object or point from which movement is determined. A system of object that are not moving with respect to one another. Must have a frame of reference to determine motion.

Choosing a Frame of Reference Relative Motion: movement in relation to a frame of reference. Most common frame of reference is Earth. Choose a frame of reference that allows you to more accurately describe motion.

Distance Distance: The length of a path between two points SI unit: meter (m) Can use kilometer (km) or centimeter (cm)

Displacement Displacement: the direction from the starting point and the length of a straight line from the starting point to the ending point Includes distance and direction Example of a vector (has both magnitude & direction) Example: Distance: the girl walked 5 blocks Displacement: the girl walked 5 blocks east

Combining Displacements Add displacements using Vector addition Straight line If 2 displacements are in the same direction-add vectors If 2 displacements are in the opposite direction-subtract vectors Not straight line Need to combine by graphing…creating a Resultant vector

SEC Speed & Velocity

Speed Speed: the ratio of the distance an object moves to the amount of time the object moves Speed = Distanceors = d Time t SI unit: meter/second (m/s)

Types of Speed Average Speed: the total distance traveled divided by the time it takes to travel that distance Ex. Average speed over an entire trip Instantaneous speed: the rate at which an object is moving at a given moment in time Ex. Speed at a given moment

Graphing Constant Speed Speed = Slope of the line

Graphing Varying Speed Speed is changing...so, slope for each section is the speed for that time

Velocity Velocity: description of both speed and direction of motion Velocity is a vector (can be added like vectors) Velocity = displacement or v = d time t SI unit: m/s

Acceleration

Acceleration: rate at which velocity changes Change in speed, direction or both Deceleration: negative acceleration an object slows down Constant acceleration: a steady change in velocity

Change in Speed Occurs when an object speeds up or slows down Direction is constant Ex. Free fall: the movement of an object toward Earth due to gravity

Change in Direction Occurs when an object changes direction Speed is constant Ex. Riding a carousel Ex. Riding a Ferris wheel

Change in Speed & Direction Occurs when there is a change in both speed and direction Ex. Riding a roller coaster

Calculating Acceleration Change in velocity divided by the total time Acceleration = (v f – v i ) t v f : final velocity v i : initial velocity SI unit: m/s 2

Graphing Acceleration Acceleration = slope of the line