After learning how to measure speed with light sensors (Speed Rolling Down A Ramp), you can now explore the relationship between kinetic energy and potential energy. In this project, you will learn how to 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 finally visualize the data in Mind+ (A graphical programming editor, mindplus.cc).
Potential Energy (PE) is the energy of position.
Kinetic Energy (KE) is the energy of motion.
In the scenario of a marble roller coaster, the kinetic and potential energy of the rolling ball is constantly converting into each other.
Expressed by equation:
K.E. = 1/2 mv^2
P.E. = mgh
Based by the conversation of energy:
mgh = 1/2 mv^2
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.
1 Micro:bit + Extension Board
1 BOSON Button Sensor
3 BOSON Light Sensors
Download the sample program 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 - heights and 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.
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.