1. Academic Enrichment 9-29-15
An object is resting motionless on a surface. According to Newton’s first law, the object will only start to move if a. the net forces on the object equal zero. b. an unbalanced force is applied to the object. c. the upward force of the object is equal to its acceleration. d. two forces that are equal and opposite are applied to the object.

2. Science Warm Up
A scientist was performing some experiments to test the designs of some simple machines. One of her experiments involved a pulley. During the experiment, a total of 2,000 J of work was done to lift a crate 5 m straight up off the floor. Ignoring the effects of friction, determine the applied force needed to lift the crate. F = W/D
400 N c. 1,995 N
10,000 N d. 2,005 N

3. Page 515 # 1-11 1st Nine Weeks Exam will be next Friday 10-9-15
Homework Due Thursday
Page 515 # st Nine Weeks Exam will be next Friday

4. Motion, Speed, and Velocity

5. GLE 0707.11.3 Distinguish between speed and velocity.

6. 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?

7. 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)

8. Graph distance on the y-axis and time on the x-axis
Graphing Motion
Graph distance on the y-axis and time on the x-axis
Slope = rise = distance = speed
run time

9. 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.

10. 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?

11. Solution Stage 1: S= d/ t 100 m/ 10 s= 10 m/s Stage 2: S= d/t
Ave Speed= Tot d/ Tot t
300 m/ 40 s= 7.5 m/s
Distance = 300 meters
Displacement = 0 meters

12. Velocity The speed and direction of an object’s motion.
88 km / hr southwest

13. Science Closure

14. Academic Enrichment Closure 9-29-15