Timing a Speedbot!
Students strengthen their communication skills about measurements by learning the meaning of base units and derived units, including speed—one of the most common derived units (distance/time). Working in groups, students measure the time for LEGO® MINDSTORMS® robots to move a certain distance. The robots are started and stopped via touch sensors and programmed to display the distance traveled. Using their collected data, students complete a worksheet to calculate the robots' (mean/average) speeds at given motor powers.
Speed and its units.Copyright (left) 2007 Brian Snelson, Wikimedia Commons; (right) 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved.http://commons.wikimedia.org/wiki/File:Ford_Mondeo_MK3_ST220_-_Speedometer.jpg
Communicating measurements is one of the most important everyday engineering and math literacy tasks. In today's cutting-edge technical applications, new types of units are frequently created to highlight a process of interest, such as a unit of speed created from the units of distance and time (foot per nanosecond, terafurlongs per fortnight, mickey per second) or a unit of density created from the units of length and mass. Base units are usually fundamental units for properties such as mass and length, and derived units are generated from combinations of units to describe the most basic observable properties of an object or situation. Understanding that base units make up derived units is essential to being a competent engineer. Another way to think about it is that derived units (such as mph) are rates of change between base units (miles = distance, hour = time). Derived units are important in science and engineering for measuring physical phenomena, and are created by performing arithmetic (such as division) on the corresponding base units.
After this activity, students should be able to:
- Define speed using the speed equation: speed = distance ÷ time.
- Identify and explain a unit of speed.
- Generate a unit of speed by combining different units of length and time.
- Calculate the speed of an object moving in a straight line by dividing the measured distance traveled by the measured time elapsed.