South Carolina ETV

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Rates in Linear Mechanical Systems (Grades 11-12)

MASTER TEACHER

Robert Sheffield

OVERVIEW

The purpose of this lesson is to introduce the students to the factors that control rates in a mechanical system. Through the use of this video, the students will discover how the relationship between distance and time determines an object's speed. Additionally, the students will observe that a change in an object's rate will result in acceleration. A follow-up activity will require the students to apply the knowledge gained in the video by determining the speed and acceleration of a passing car.

ITV SERIES

Principles of Technology, Lesson 3: Rates

LEARNING OBJECTIVES

The students will be able to

identify the units associated with speed
calculate the speed of a moving object
identify the units associated with acceleration
calculate the acceleration of a moving object

SC MATH/SCIENCE STANDARDS MET

This lesson will provide the students with additional exposure to the following standards:

Make quantitative observations
Recognize the limitations of measuring devises
Analyze data to construct conclusions
Explain sources of error in investigations

MATERIALS
(per group)

stop watch (3)
measuring tape (1)
calculator (1)
orange athletic cones (4)

PRE-VIEWING ACTIVITY

Conduct a brain-storming session. The prompt for the class would be: " Name all the rates you are familiar with." (Answers may include miles per hour, meters per second, and heart beats per minute). Then ask the students to identify the common factor in all rates. The students should be made aware that all rates are an event divided by time.

FOCUS FOR VIEWING

To give the students a specific responsibility while viewing the video, have them watch for the different units associated with speed and acceleration. Inform the class that during the video they will be asked to defend and justify the use of the different units. For example: Given the unit miles/hour - the student would identify this as a unit of speed because it is a unit of distance divided by a unit of time.

VIEWING ACTIVITIES

The video begins with a scene of two drag racing cars preparing to race and the title screen "Rates in Mechanical Systems."

Pause the video when the announcer asks the question, "Who won the race?" and answers himself, "The one with the faster rate." The teacher should ask the class, as a reminder, what is a rate? And to predict which rate he is referring to? Resume video.

Pause the video when the scene of the filling milk jugs is completed and have the students suggest units for the rate shown. Resume video.

Pause the video when the equation "speed = miles/hour" is shown and have the students defend the use of these units. Resume video.

Pause the video when the private jet is preparing to take off. Inform the students that in the upcoming segment, the dots represent equal time intervals. Turn off the sound and allow the video to continue. Three individual scenes will follow of the airplane traveling from left to right across the screen. The students should predict, after each scene, if the rate of the airplane is changing and how it is changing. After the screen of the three different accelerations shown simultaneously, rewind the video and show the scenes over with sound. This allows the students to assess their predictions.

Pause the video on the frame of "a=m/s/s." The teacher should ask the students to justify or defend the use of these units.

Pause the video on the frame of "a=m/s2" The teacher should ask the students if they understand the simplification of "a=m/s/s" to "a=m/s2."

Fast forward the video through the segment on rotational mechanical rates, and continue with the scene from the Norfolk Southern Railroad yard.

The video concludes with a black and white scene of a car rolling over a cliff.

POST VIEWING ACTIVITY

In groups, the students will calculate the speed of a passing automobile. The group's calculations will be used in conjunction with other groups to determine the acceleration of the passing car. Use Activity Sheet 1.

ACTION PLAN

As a follow up activity; have the students investigate and determine the speed of light and sound using the Internet as a reference. Have ,them compare the two speeds and apply this new information to explain why the sight of lightning usually precedes the sound of thunder.

EXTENSIONS

Additional activities that can be generated from this lesson:

Earth Science: Calculating the rate of the motion of glaciers.

Chemistry: The effect of a catalyst on the rate of a chemical reaction.

Biology: Finding the rate of heart beats per minute.

Math: Solving algebraic equations and isolating multiple variables.

Math: Using dimensional analysis to convert units.

Activity Sheets (PDF)

Activity Sheet 1