1. Unit II – Speed, Motion, Velocity and Acceleration
Physical Science
Unit II – Speed, Motion, Velocity and Acceleration

2. Describing Motion

3. Motion For Motion to occur, the position of an object must change
Its Displacement is the difference in position

4. Displacement
Displacement (or change in position) is measured in the SI unit meter m.
What is the displacement of a runner that jogs 100m and back?
What is the displacement of a runner that jogs 100m in one direction?

5. Solving Motion Problems
Use scientific formulas to solve for variables.
Ex: what is the speed of a rabbit that travels 1.3 km in 30 min?

6. Speed Speed is equal to change (Δ) in distance divided by time.
Abbreviated equation s = d t
Common units for speed:
mph (miles per hour)
m/sec (meters per second)
km/hr (kilometers per hour)

7. Calculating Speed
What is the speed of a car that travels 80 km in 2 hours?

8. Speed = distance s = d
time t
Speed = 80 km
2 hours
Speed = 40 km/hr

9. Solving motion problems
Remember to set up problem to solve for x
Remember all variables in a formula have a unit of measurement
Change the formula around to solve fore the variable that you want.
s=d/t d=st t=d/s

10. Average Speed and Instantaneous Speed
Average speed is total distance divided by total time.
ex: If you travel 50 meters in 10 sec, your average speed is 5 m/sec
Instantaneous speed occurs while an object is in motion.
ex: think of your speedometer on your car

11. Graphing motion Place time on the x – axis
Place distance on the y-axis
Label units
Connect points to show a trend
The slope of the line is your speed!

12. Velocity What is velocity? Speed with a direction EX: 12 m/sec west
52 mph down
8000 m/sec forward
A unit of speed is assumed to be velocity if the direction of motion is obvious

13. Solving velocity problems
What is the velocity of a water balloon that falls 16m in 3.2 sec?
S=d/t
S = 16/3.2
Velocity = 1.88 m/s down