1. Motion Measuring Motion Motion Speed & Velocity Acceleration
SPS8. Students will determine relationships among force, mass, and motion.
Calculate velocity and acceleration.
S8P3. Students will investigate relationship between force, mass, and the motion of objects.
a. Determine the relationship between velocity and acceleration.
Measuring Motion
Motion
Speed & Velocity
Acceleration

2. Motion
Motion is when an object changes position over time relative to a reference point.
Problem:
Is your desk moving?
We need a reference point...
a nonmoving or moving point from which motion is measured

3. Motion Motion Change in position in relation to a reference point.

4. s d t Speed Speed rate of motion
distance traveled by an object in a given amount of time
Write Formula

5. Speed Instantaneous Speed speed at a given instant Average Speed
Write Formula

6. Velocity Velocity speed of an object in a given direction
changes when speed and/or direction changes
considers displacement
Examples:
The car’s velocity was 104 km/h N (about 65 mph N).
John’s velocity was 1 m/s S (about 2.2 mph S)
The runner’s velocity was 37 km/h W (about 23 mph W).
Write the formula

7. t a Acceleration Acceleration the rate of change of velocity
vf - vi t
Acceleration
the rate of change of velocity
change in speed and/or direction
Write Formula
a: acceleration
vf: final velocity
vi: initial velocity
t: time

8. Acceleration The velocity can change even when the speed is constant!
Examples:
25 m/s S  25 m/s E
55 m/s W  20 m/s W

9. Acceleration Acceleration can also mean changing DIRECTION.
When a car goes around a curve, it accelerates (even if it does not speed up or slow down).

10. Acceleration Positive acceleration “speeding up” Ex. 5 km/h  25 km/h
Negative acceleration (Deceleration)
“slowing down”
Ex. 25 km/h  5 km/h

11. Acceleration
Acceleration is the rate at which an object changes its velocity (speed AND direction).
Acceleration has nothing to do with going fast. A person can be moving very fast and still not be accelerating.
Speeding up, slowing down, and/or changing direction are all acceleration.
Which of the cars are accelerating?
Only the green & blue are accelerating!
The red is at a constant motion.
The blue has the greatest acceleration!