Linear Kinematics: Describing Objects in Linear Motion

Objectives:
  • Distinguish between linear, angular, and general motion
  • Define:
    • Distance and displacement
    • Average speed and average velocity
    • Instantaneous speed and velocity
  • Name units of measurement for above definitions
  • Use equations of motion for projectiles

Kinematics is the branch of dynamics concerned with the description of motion.

Ben Johnson versus Carl Lewis
Data from some of the fastest races ever

Linear motion

Angular Motion
General Motion

Animation of linear and angular motion

Is a runner 40 m from the start or 60 m from the finish?

Where does the tighthead prop and hooker line up in rugby union?

x, y, z, rotationx, rotationy, rotationz

Slope of a position-time graph

Comparing position and velocity graphs

SPEED vs VELOCITY
Average Speed and Average Velocity Equations

Marathon speed

What was a marathon runner's average speed in finishing the 42.2 km race in 2 hours 11 minutes?

A rowing shell was progressing across stream in the Willamette River at 8 mph relative to the water, while the river was flowing at 6 mph. What was the velocity of the shell with respect to the bank?
Pacing Example

What about changing speeds and velocities?

Average Acceleration Equation
What does this imply for running around a curve?
Is someone accelerating when running a constant speed around a curve?

Shot Put Example
Position-Time Data


Velocity-Time Data

Slope of velocity-time graph equals acceleration

Corrected

Displacement with intial velocity and with constant acceleration
d=vit + 0.5at2

Bobsled Example


What is the average speed if you run a kilometer at 5 m/s and then walk a kilometer at 1 m/s ? (Note: 3 m/s is not correct.) Solution