Kinematics The study of how objects move

Where are You? We must start with a question

Position Reference Point: Zero location in a coordinate system or frame. Frame of Reference: Coordinate system used to define motion. Position: Separation between an object and a reference point. It needs a distance and direction. i.e. 3.0 meters to the right. To find where you are you need the following:

You are Here

Distance vs. Displacement Distance is simply the total path length traversed in moving from one location to another Distance is a SCALAR quantity. A measurement with only magnitude, or size. 50 m

Distance vs. Displacement Displacement is the straight-line distance between two points, along with the direction from the starting point to the final position. Displacement is a VECTOR quantity. A measurement with magnitude, or size and a direction 10 m East

Difference between Distance and Displacement Walking to Physics Lab Distance = 8 m Displacement = 8m right Right - Positive Left - Negative Direction Convention : Displacement =+8m

Speed Speed is the rate at which distance is traveled. =10 m/s 20 m 2 sec Speed is a scalar quanity

Average speed Average speed is the distance d traveled, the actual path, divided by the total time t elapsed in traveling that distance. Instantaneous Speed Instantaneous Speed is how fast an object is moving at a particular instant of time. Average vs. Instantaneous Speed

VelocityVelocity tells how fast something is moving and in what direction. Velocity is a vector quantity. Average Velocity Average Velocity is the displacement divided by the total travel time =initial position, commonly zero = initial time, commonly zero When x o and t o are zero

A jogger jogs from one end to the other of a straight 300 meter track (from point A to point B) in 2.50 min and then turns around and jogs 100 m back toward the starting point (to point C) in another 1.00 min. What are the jogger’s average speeds and velocities in going A) From A to B B) From A to C after turning around Speed and Velocity Problem

A) Given: x B = 300m - 0m = +300m (from A to B) x C = 200m – 300m = -100m (from B to C) t B = 2.50 min = 150 s t C = 1.00 min = 60.0 s B) Average speed and velocity from A to B Average speed and velocity from A to C

Two Component s of Velocity

Graphical look at Motion

Acceleration Position is the separation between an object and a reference point. Displacement is a change in position Velocity is the time rate change of displacement Acceleration is the time rate change of velocity All four are vector quantities Represented by a magnitude and direction

KinematicEquationsKinematicEquations

accelerationvelocity

With a constant acceleration Total Displacement and total time Average Velocity

KinematicEquationsKinematicEquations

Problem: Ally the Alligator takes off from an airfield. She starts from rest and obtains a velocity of 36 m/s at take off in 20.0 seconds. What is her acceleration down the runway? How far did she go down the runway?