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This project will teach you how to use BOSON light sensors to make a timing gate that measures the speed of a rolling ball. You can apply the same method on a ramp to test out the famous Galileo's inclined plane experiment, or explore the relationship between kinetic energy and potential energy on a curvy track. And visualize the data in Mind+ (A graphical programming editor, mindplus.cc).
How to Measure Speed:The light sensor measures light intensity. We use light sensors in this project to detect the ball passes by based on a drop of light value.
Place the sensors every 10cm (Distance).
Record the time of the ball passing through the sensors respectively, then calculate the interval time by time2 - time1(Time).
We can get the average speed of the ball with: Speed = Distance / Time.
Potential Energy (PE) is the energy of position.
Kinetic Energy (KE) is the energy of motion.
Expressed by equation:
K.E. = 1/2 mv^2
P.E. = mgh
Based by the conversation of energy:
mgh = 1/2 mv^2
In the scenario of a marble roller coaster, the kinetic and potential energy of the rolling ball is constantly converting into each other.
The horizontal track is a simple model to explain how to measure the speed of a rolling ball. It consists of 2 light sensors placed 10cm in between and plugged into a micro:bit to collect and visualize the data in a Mind+ program.
Make the Model:
1.Prepare the long sides of the track from cardboard. Cut out 2 slots about 2.5cm x 1cm for sensors 10cm apart.
2.Prepare the bottom in the same length of the side and 2.5cm wide.
3.Prepare the short sides 2.5cm wide and higher than the track to stop the ball from rolling.
4.Glue everything together.
Connect Hardwares:
Download the sample program 1 and open it. Click connect hardware on the top and choose micro:bit port. (If there is no micro:bit port showed up, try to re-plug the micro:bit to your computer.)
Click the green flag to start the program.
In this program, the distance is set to 0.1m. After the ball passes by and get t1 and t2, the speed will be calculated automatically.
After understanding how to measure the speed, you can apply the same method and upgrade the model into a inclined plane. The model uses a button to start timing, and places 3 light sensors to measure the average speed of three sections.
Make the Model:
Connect Hardwares:
Download the sample program 2 and open it in Mind+. Press the ball against the button and let go. After the ball passed each sensor, the average speed of 3 sections will be shown and visualized in a line chart.
Conclusion:
The ball accelerates down a ramp.
Activity 3: Marble Roller CoasterAfter understand how to measure speed with light sensors, you can now build a roller coaster track with cardboard and embed the sensors, then measure the speed and height to calculate the kinetic and potential energy, and visualize the data.
Make the model:
The project uses a button sensor to set the timer and record the speed the ball rolls down using 3 light sensors.
The key to designing the roller coaster track is to place the light sensors at the same distance in between, 10cm is recommended, then the speed can be easily calculated by speed = time/distance (10cm).
You can download the printable and trace the shape, or design your own track.
Download the sample program 3 and open it in Mind+. Click connect hardware on the top and choose micro:bit port. (If there is no micro:bit port showed up, try to re-plug the micro:bit to your computer.)
Click the green flag to start the program.
You will see the graph of potential energy is automatically generated.
In the program, the height of the sensors is pre-imported, then multiple the height value by G (10) to calculate the potential energy (mgh). Since we only need to explore the relationship between potential and kinetic energy instead of getting a precise value, the mass of the ball can be omitted (gh = ½ v^2). If your track looks different, just go to Variables - Make a list - heightsand change the values.
Press the ball against the button and let go. The timer starts when the button is released as soon as the ball rolls down. When the ball passed each timing gate, the speed is recorded, and the kinetic energy is calculated and visualized in a graph.
Conclusion:
From the graph, it is clear that when kinetic energy rises, potential energy decreases and vice versa. Therefore we can say, potential energy and kinetic energy can be converted into each other. But because of friction, energy will be lost in the process.
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