distance sensor or sonar ranger
These distance or motion sensors use sound reflected from an object to detect changes in its position. Most designs were based on the sensor developed as the range finder for Polaroid’s cameras. You can walk towards the sensor and watch a graph of your displacement, velocity or acceleration appear on the screen. It is usual to put a graph on the screen and then get students to try to create one on top of it. You can point one at a swinging pendulum; or suspend them under a mass on a spring. You can also hold one above a bouncing ball and show the bounces, though they tend to look upside down because down is far away from the sensor. By most accounts, this is a very useful sensor to learn from – it is worth getting hold of some teaching materials to see its great scope. The range finder sensor component inside is fairly expensive so these will not be cheap. Do use them with a power transformer as they eat batteries. The range is typically from 50 to 500 cm – go too close and they get confused. There are limits on how fast they record so light gates are still useful for measuring fast changes. A force or dynamics pulley offers much better accuracy should you need it. Lots of activities for these nearby – look for ‘distance sensor’.
- direct measurement of distance.
- preparing distance-time graphs
- calculating kinetic energy, acceleration and speed: when walking, cycling, moving trolleys, bouncing a ball.
- oscillator motion (with a spring held weight).
- studies of an air track puck; friction studies. Conservation of momentum.
- investigations into the design of a ski jump,
- stopping distances of model cars.
- acceleration due to gravity.
I’ve rated these sensors but your assessment will be different. I give a score, out of five, for the sensor’s intrigue, interest, and learning potential. I also give a score for how often a science department might use it.