Physics

1
Physics
Motion, Speed, and Velocity
2
SC Standards Covered

• PS-5.1
• Explain the relationship among distance, time,
  direction, and the velocity of an object
• PS 5.2
• Use the formula vd/t to solve problems related
  to average speed or velocity
• PS 5.6
• Represent linear motion of objects on distance
  time graphs

3
Motion

• When an object changes its position, motion has
  occurred.
• Distance- How far an object has moved.
• Displacement- How far an object has moved in
  relation to its starting point.
• Consider direction
• Example Two runners travel along the same
  straight path in a straight line for 500 meters.
  At the end of the run their distances are the
  same but their displacements are different. How
  can this be so?

4
Speed- Distance an object travels per unit of
time

• Relationships between speed, distance, and time
• Speed Distance/ Time d/ t
• Constant Speed- speed does not change over time
• Average Speed- speed of motion when speed is
  changing
• Avg Speed Total Distance/ Total Time
• Instantaneous Speed- speed at any given moment in
  time (speedometer)

5
Graphing Motion

• Graph distance on the y-axis and time on the
  x-axis

• Slope rise distance speed
• run time

6
Distance - Time Graph

• If something is not moving, a horizontal line is
  drawn.
• If something starts out slow and then speeds up,
  its change in speed can look like this.

7
Learning Checkpoint

• This graph shows several stages of motion
• Stage 1 100 m in 10 s
• Stage 2 50 m in 10 s
• Stage 3 150 m in 20 s
• Calculate the speed as indicated by each of the
  colors.
• Calculate the average speed.
• What is the total distance?
• What is the displacement?

8
Solution
Stage 1 S d/ t 100 m/ 10 s 10 m/s Stage 2
S d/t 50 m/ 10 s 5 m/s Stage 3 S d/t 150 m/
20 s 7.5 m/s Ave Speed Tot d/ Tot t 300 m/ 40
s 7.5 m/s Distance 300 meters Displacement 0
meters
9
Velocity

• The speed and direction of an objects motion.
• 88 km / hr southwest