8/29/2008 5:56:00 PM
Displacement
 Defined as the change in position during some time interval o Represented as changeinX
 Changeinx=final-initial
 SI units are meters, and changeinX can be positive or negative o Can be different than the distance traveled- the length of a path followed by particle
Vectors and Scalars
 Vector quantities need both magnitude (size or value) and direction
Average Velocity
 The average velocity is rate at which the displacement occurs
 V(Average)=(Change in X)/(Change in Time)
 The dimensions are length/time [L/T}
 SI units are m/s
 Is also the slope of the line in the position- time graph
Average Speed is a scalar quality
 Same units as velocity
 Total distance/total time
 The average speed is not always the same as the average velocity
 Speed is always positive
 Average Speed is the average velocity of the total distance traveled
Instantaneous Velocity
 The limit of the average velocity as the time interval becomes infinitesimally short, or as the time interval approaches zero
 The instantaneous velocity indicates what is happening at every point of time
Instantaneous velocity equation
 V(x)=lim(changeT>0)[changeX/changeT]=dx/dt
 The instantaneous velocity is the derivative of the displacement equation
 The instantaneous velocity is the slope of the line tangent to the x vs t curve
Instantaneous Speed
 The instantaneous sped is the magnitude of the instantaneous velocity

 Remember that in general the average speed is not the magnitude of the average velocity
Average Acceleration
 Acceleration is the rate of change of the velocity
 A(x)=changeV/changeT
 Dimensions are L/T^2
 SI units are m/s^2
Instantaneous Acceleration
 The instantaneous acceleration is the limit of the average acceleration as changeT approaches 0
Acceleration and Velocity, 1
 Hen an object’s velocity and acceleration are in the same direction, the object is speeding up
 When an objects velocity and acceleration are in the opposite, the object is slowing down
 An object can be moving very fast but have no acceleration
 Acceleration and Velocity can be the same or opposite signs
Kinematics Equations summary
 Velocity as a F(time)
 Position as a F(V,T)
 Position as a F(T)
 Velocity as a F(P)

29.08.2008 17:56:00

29.08.2008 17:56:00