Essential Question: How is energy conserved? Energy and Motion Essential Question: How is energy conserved? -What is acceleration? -How do you graph acceleration? 8.5 Acceleration Pgs. 314-319

Vocabulary 8.5 Acceleration- The rate at which velocity changes.

What is Acceleration? Pg. 314 When you think about acceleration, what is the first thing you think of?? Acceleration means “the process of speeding up.” r. p314 Scientists define acceleration as the rate at which velocity changes. In science, acceleration refers to increasing speed, decreasing speed, or changing direction.

Changing Speed pg. 315 Whenever an object’s speed changes, the object accelerates. The change in speed can be either to speed up or to slow down. Slowing down is sometimes called deceleration (negative acceleration.) Example: Red Light= car slows down

Changing Direction pg. 315 Even an object moving at constant speed can be accelerating—as long as it is changing direction. Acceleration= change in direction and a change in speed Example: car going down a hill (speed/accelerates) and then it changes lanes (direction/different lanes) There are many objects that move continuously change direction without changing speed. Example : Ferris wheel

What is Acceleration? Pg. 316 Acceleration describes the rate at which velocity changes. If an object is NOT changing direction, you can describe its acceleration as the rate at which its speed changes. To determine the acceleration of an object moving in a straight line, use the following equation. Acceleration = Final Speed – Initial Speed Time If speed is measured in meters per second (m/s) and time is measured in seconds, the SI unit of acceleration is meters per second per second, or m/s2.

Figure 2. Acceleration pg. 316/17 The airplane is accelerating at a rate of 8 m/s2. Determine the speed of the airplane at 4.0 s and 5.0 s. 0 m/s 8 m/s 16 m/s 24 m/s

Figure 3 –Acceleration PG. 316 Deceleration The airplane touches down with a speed of 70 m/s. It decelerates at a rate of -5 m/s². Determine its speed after each second of its deceleration.

How Do You Graph Acceleration? Pg. 318 You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object. The slope of the speed-versus-time graph is the acceleration. A slanted straight line on a speed-versus-time graph means that the acceleration of the object is constant, but not zero. If the line slants upward, speed was increasing. If the line slopes downward, speed was decreasing.

Fig. 4 –Acceleration pg. 318 Speed-Versus-Time Graph Use the time and speed data in the table to plot a line graph. Plot time on the horizontal axis. Plot speed on the vertical axis. What would be a good title for the graph? What is the slope of the graph?

Figure 5—Acceleration g. 319 Distance-Versus-Time Graph Use the time and distance data in the table to plot a line graph. Plot time on the horizontal axis. Plot distance on the vertical axis. What would be a good title for the graph? How does the distance change with time? ______________________________________________________