Lesson 1.5: Graphical Description of Accelerated Motion
Completion requirements
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Lesson 1.5: Graphical Description of Accelerated Motion
When taking a short trip in a vehicle, you will see the speedometer change as you travel. This indicates that you are not travelling with uniform motion. The vehicle’s motion is non-uniform and involves accelerated motion.Acceleration is a change in velocity. that can mean a change in speed or a change in direction. IN Science 20 we consider only changes in direction. A negative change in speed - something is slowing down - is called deceleration.
You should be able to recognize acceleration of potion-time, velocity-time and acceleration -time graphs.
You should be able to recognize acceleration of potion-time, velocity-time and acceleration -time graphs.
- Read pages 194 and 195 of the textbook, ending at “A Graphical Description of Accelerated Motion”.
- Read “A Graphical Description of Accelerated Motion” at the bottom of page 195 of the textbook. Please take the time to do the following ticker tape timer activity.
- Read the entire investigation on pages 196 and 197 of the textbook.
If you have access to a supervised laboratory and a partner to help you, do Path 1. If you do not have access to these resources, do Path 2. This activity is very valuable and helps many students understand acceleration.
- Follow the directions in the investigation. Ideally, use a long table or board (at least 1.5 m long) with one end raised approximately 4 to 8 cm.
- Answer questions 1 to 7 on page 197.
Check your answers with those in the “Suggested Answers” in the online course.
For this path you will watch two students carry out this investigation.
- Make predictions to the questions posed in the purpose.
- View Part A of “Accelerated Motion—Part A Speeding Up, Part B Slowing Down” . Stop and start the video as required.
- Use the sample data for this investigation in the “Suggested Answers” in the online course to answer questions 1 to 7 on page 197. Check your answers with those in the “Suggested Answers” .
- Read pages 198 to 199 of the textbook. Make sure you work through Example 1.10 on your calculator. Do Practice Problem 24 and check your answers with those in the “Practice Answers” .
Acceleration is measured in units of distance /time2. For example, m/s2.
The graphs below show uniform acceleration.
The slope of a velocity time graph gives acceleration. So the equation for acceleration is: «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mi»a«/mi»«mo»§#160;«/mo»«mo»=«/mo»«mo»§#160;«/mo»«mfrac»«mrow»«mi»§#916;«/mi»«mi»V«/mi»«/mrow»«mrow»«mi»§#916;«/mi»«mi»t«/mi»«/mrow»«/mfrac»«/math»
The graphs below show uniform acceleration.
Read page 199 - 200. work through the Example problems and do Practice problem 25. Check your answers with those in the “Practice Answers”
Galileo studied the uniform acceleration of falling objects. The problem he had was measuring time. Objects fall too quickly to take meaningful time measurements using the pendulum device he had. The solution to this problem was to slow falling objects down.
He used ramps to slow the falling motion down so it could be studied.
He used ramps to slow the falling motion down so it could be studied.
Try using a ramp in the investigation below if you want to try it. How could a ramp be used to investigate negative acceleration?
- Read “Another Way to Think About Acceleration” at the top of page 201 of the textbook.
Figure 1.5a: Galileo's ramp. Wikipedia
- Read the entire investigation on page 201 of the textbook.
If you have access to a supervised laboratory and a partner to help you, do Path 1. If you do not have access to these resources, do Path 2.
- Follow the directions in the investigation, answer the questions.
Check your answers with those in the “Suggested Answers” in the online course.
For this path you will watch two students carry out this investigation.
- Make predictions to the questions posed in the purpose.
- Answer question 1 of “Design” on page 201. You may do this by yourself.
- View Part B of “Accelerated Motion—Part A Speeding Up, Part B Slowing Down” . Stop and start the video as required.
- Use the sample data for this investigation in the “Suggested Answers” in the online course to answer questions 3 to 9 on page 201.
Check your answers with those in the “Suggested Answers” in the online course.
In the preceding investigation, the cart was slowing down; yet it was accelerating. You may have thought that an accelerating object is one that is speeding up. But that is not necessarily true. From a scientific point of view, a vehicle is actually
accelerating when its driver steps on the brake pedal to slow down. During braking, the acceleration vector points in the opposite direction of the velocity vector. That is, the car is undergoing negative acceleration.
When talking about everyday situations, people generally think about only positive acceleration when using the word acceleration. This conversational practice can stand in the way of a full scientific understanding of acceleration as any change in velocity.
Note that an object slowing down—such as a car coming to a stop—may be said to be decelerating.
When talking about everyday situations, people generally think about only positive acceleration when using the word acceleration. This conversational practice can stand in the way of a full scientific understanding of acceleration as any change in velocity.
Note that an object slowing down—such as a car coming to a stop—may be said to be decelerating.
- Read page 202 of the textbook and work through the example problems. Do Practice questions 26 to 28 on page 203, and check your answers with those in the “Practice Answers” in the online course.
- Read “1.5 Summary” on pages 203 and 204 of the textbook. Then, complete “1.5 Questions” and check your answers with those in the “Practice Answers” in the online course.