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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.
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SPEED, VELOCITY AND ACCELERATIONMotion
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. 11.2Speed & Velocity
Speed• Speed: the ratio of the distance an object moves to the
amount of time the object moves
• Speed = Distance or s = 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• 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)
tvf: final velocity
vi: initial velocity• SI unit: m/s2
Graphing Acceleration
• Acceleration = slope of the line