Describing Motion

1. Describing Motion 1-D Kinematics

2. Kinematics • Science of describing motion. • Words • Diagrams • Numbers • Graphs • Equations • Develop sophosticated mental models that describe the motion of real-world objects.

3. Coordinate Sytems • System used to describe motion that indicates when the zero point of the variable is located and the direction in which the values of the variable increase. • Origin: point in which the variable has a value of zero. • Position vector: arrow used to identify the position of the moving object at any given time. • Length of the position vector is proportional to the distance of the object from the origin and points of origin to the location of the moving object at a particular time.

4. Scalars • Quantities that are described by magnitude (numerical value) only. • Time • Mass • Temperature

5. Vectors • Describe magnitude and direction • Acceleration • Velocity

6. Distance and Displacement • Distance: scalar quantity. It is referring to how far an object moves “distance covered”. • d0 to d1 • Displacement: vector quantity. Refers to the distance and direction Δd = d1 – d0

7. 1 1 Distance vs Displacement

8. Velocity vs Acceleration • Velocity: speed and direction that an object moves. • Vector quantity • Speed =distance traveled/time of travel s = d/t • Velocity = Δposition/time = Δd /Δt • Instantaneous speed is speed at any given point of time. • Average speed – average of all instantaneous speeds.

9. Acceleration: rate at which an object changes it’s velocity. • Vector quantity • Constant Acceleration : when an accelerating object changes Its velocity by the same amount each second. • Average acceleration = Δ velocity/time or a = vf - vi / t