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 1998 Olympic Games
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?
How is a Aussie Rules Football player's location on the field described (Center Full Forward)?
x, y, z, rotationx, rotationy, rotationz
Slope of a position-time graph
Comparing position and velocity graphs
SPEED vs VELOCITY
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 Examples
What about changing speeds and velocities?
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
Displacement with intial velocity and with constant acceleration
d=vit + 0.5at2
Bobsled Example
Cavanagh, P.R. & Kram. R. (1989). Stride length in distance running: velocity, body dimensions, and added mass effects.
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
Projectile Motion
A Projectile is any body that has been set on its path by some force and continues in motion by its own inertia. (Gravity has a major effect on motion).
Examples of Projectiles include: Arrow, Basketball, Shotput, Human Body,Tigers
Let's begin simply with purely vertical motion
Now let's add horizontal motion
Horizontal and vertical components are independent
Equations of motion for projectiles
Characteristics of projectiles
Demonstration on what happens as initial conditions are altered
Another projectile cartoon
Practice Question:
Initial Velocity of Projectile
Vh = 5 m/s
Vv = 10 m/s |
Flight Time = ?
Maximum Height = ?
Horizontal Displacement = ? |
Practice Question:
Initial Velocity of Projectile
V = 20 m/s
at 45 degrees |
Flight Time = ?
Maximum Height = ?
Horizontal Displacement = ? |
Things get more complex when takeoff and landing heights are different
Shot Put Example
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