1. Chapter 2—Motion and Force
Section 1—Describing Motion
Resource Science

2. Motion and Speed
Motion—occurs when an object changes its position
*Motion doesn’t always have to be seen to have taken place

3. Distance and Displacement
Distance—describes how far something has moved
SI base unit to measure distance is METER
Displacement—the distance and direction of an object’s change in position from the starting point
See figure 2 on pg. 39

4. Speed Speed-the distance an object travels per unit of time
Ex: miles per hour/ feet per minute, etc.
Rate—any change over time, so--
**Speed is a RATE
Equation: Speed = Distance / Time
(typically measured in m/s)

5. Practice Calculating Speed-pg. 42-# 1 and 2
*Most speeds aren’t constant, they either slow down or speed up
Average speed-describes speed of motion when speed is changing
(driving on a 3 hr. trip)
Instantaneous Speed-speed at a given point in time
Ex: speed on a speedometer

6. Velocity
Velocity--includes the speed of an object AND the direction of its motion
*Velocity can change EVEN IF speed remains constant
Change in Velocity—can be EITHER a change in speed OR in direction of movement

7. Remember:
*To Calculate Velocity, it is the same as calculating speed, but you must also report a DIRECTION-north, south, east, west, etc.
*One example of change in velocity—when a race car at a constant speed is rounding a curve, velocity is changing, due to direction of travel changing

8. Section 2—Acceleration
Acceleration-the rate of change of velocity (velocity = speed w/direction)
When the velocity of an object changes, the object is accelerating
So: Acceleration occurs when an object changes its SPEED, its DIRECTION or BOTH

9. If speed is increasing = positive acceleration (acceleration)
If speed is decreasing = negative acceleration (deceleration)
Ex: horse on a carousel-acceleration due to direction only

10. Amusement Park Acceleration:
Wooden and steel roller coaster provide different thrills due to different materials
Wooden-swaying effect
Steel-more loops, steep inclines, drops, etc.