Domino Dash (Jessica Goforth)
Title: Domino Dash: Finding Average Speed
Principle(s) Investigated: Average speed, collecting data
Focus on Physical Sciences
8.1.b Students know that average speed is the total distance traveled divided by the total elapsed time and that the speed of an object along the path traveled can vary.
8.1.c Students know how to solve problems involving distance, time and the speed of an object.
Investigation and Experimentation
8.9.e Construct appropriate graphs from data and develop quantitative statements about the relationship between variables.
8.9.f Apply simple mathematical relationships to determine a missing quantity in a mathematical expression, given the two remaining terms.
Math Standards
Algebra and Functions 6.2.3 Solve problems involving rates, average speed, distance and time.
Materials: Dominoes- Target, Wal-Mart etc..
Meter Stick- supply closet
Stop Watch- Google Gadget, Sporting good stores, Wal-Mart/Target
Procedure:
This lab utilizes students for most of the set-up so the instructor just needs to make sure there is an adequate amount of materials for the class. Groups can be large or small depending on class size and available resources.
1. After reviewing the concept of distance and time, explain one relationship between them is known as average speed.
a. Average Speed is the rate of motion. Calculated by dividing the total distance by the total amount of time.
b. Provide examples:
i. If a car's average speed is 65 miles per hour, this means that the car's position will change (on the average) by 65 miles each hour.
ii. Speed can change along the path taken because average speed is total distance over total time.
2. Handout worksheets
3. Go over procedure
Directions to students:
1. Set up all 25 dominoes with equal spacing between them. Set the dominoes in a straight line to cause a chain reaction when the first domino is pushed.
2. Measure the length of the domino row. Record this data in the table.
3. Use the stopwatch to measure the time it takes for the entire row of dominoes to fall after the first domino is pushed. Record the data on your worksheet.
4. Calculate the speed at which the dominoes fell. Record.
5. Set up another row of a different length, with dominoes spaced evenly. Predict how the average speed will change as the distance changes Repeat steps 2 – 4.
6. Repeat for a total of 5 different trials. Record data on handout.
After all trials have been completed and average speed has been calculated-
Record your data here!
Student prior knowledge:
Students should understand the basic difference between speed and acceleration. – Acceleration involves a force that causes a change in speed or a change in direction.
Explanation: Give a thorough explanation of the experiment or demonstration. Your explanation should be written to give your fellow teachers a solid understanding and include greater detail than what you might provide for your secondary students. Make certain to include equations whenever pertinent.
This lesson focuses on average speed by asking students to find the components of, and solve for, average speed. Students should be able to solve problems involving distance, time and the speed of an object.
Working in groups, students will create a row of dominoes and measure the length of the row. They will then time how long it takes from when the first domino is pushed to when the last domino falls. They will record distance and time on the handout. Students should realize finding these two components allows them to calculate average speed. Using the data collected, students will find average speed for 5 different trials (length of the row will change each trial).
Emphasize that although time may be longer for longer distances, the dominoes could actually have a faster average speed. Likewise shorter distances with shorter times could have a slower average speed. From the information students collect, point out that there appears to be an optimal length for the dominoes resulting in a faster average speed than at other lengths.
Conclude the lesson with a few simple problems to check for understanding. Also, provide examples of when average speed is used in everyday life. (Planning trips, distance events...)
Questions & Answers:
Question: If a person can walk with an average speed of 2 meters/second, how far will they walk in 4 minutes?
Answer: There are 60 seconds in 1 minute, so there are 4 (60 seconds) = 240 seconds in 4 minutes. Also, if average speed = distance/time, then distance = (average speed)(time). Therefore, the distance the person moves is (2 m/s)(240 s) = 480 meters.
Question: A car travels between 2 towns 60 miles apart in 2 hours. What is its average speed?
Answer: average speed = distance/time Therefore, the average speed of the car is 60 miles/2 hours = 30 miles/hour
Question: Does average speed make any indications about direction?
Answer: No, speed does not indicate direction. Velocity is a measure of magnitude and direction.
Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.
Speed limits: If you are pulled over going 80 mph in a 65 mph zone, you can not get out of a ticket by saying “but my average speed was 60mph!” The speed you are being punished for is the instantaneous speed you were going at a particular moment.
Planning Trips: While planning a trip to Grandma’s house 95 miles away, you might be interested to know what your average speed will be. Why? If you can estimate your average speed you can estimate how long it will take for you to get there. If your average speed is 60mph, 60=95miles/time. = 1.6 hours
Distance events: Average speed can be used to train or compete in many distance events. A runner competing in the mile run needs to know their average speed per lap to pace effectively. For example, running each lap at 1.5 minutes will result in a minute mile. Average speed can be calculated at the end of a race also by taking the total distance (1 mile) / time (6min) to give you .17 miles/minute.
Swim Sets: 10x200's with 10 seconds rest in between. Take the total time minus 90 seconds (for each ten second rest). Using this information use the formula average speed= distance/time to calculate average speed.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.