SPEED VELOCITY AND ACCELERATION Motion Distance Displacement Frame

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. 11. 2 Speed & Velocity

Speed • Speed: the ratio of the distance an object moves to the amount of time the object moves • Speed = Distance or Time s=d 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 time • SI unit: m/s or v=d t

Acceleration

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 = (vf – vi) t vf: final velocity vi: initial velocity • SI unit: m/s 2

Graphing Acceleration • Acceleration = slope of the line