Human Power
How much of your own "person power" does it take to equal a horse?Copyright (left) NASA http://mix.msfc.nasa.gov/abstracts.php?p=2631 (right) US National Library of Medicine http://dietarysupplements.nlm.nih.gov/dietary/women.jsp
Students do work by lifting a known mass over a period of time. The mass and measured distance and time is used to calculate force, work, energy and power in metric units. The students' power is then compared to horse power and the power required to light 60-watt light bulbs.
The basic concepts of work, force, energy and power are fundamental physics concepts utilized in many engineering calculations and design. Every engineered device that moves, lifts or pushes requires energy. Engineers must know how to calculate the power and energy needed to do the necessary work or provide the required heat. Most of the world uses metric units to quantify engineering terms. But the US is still one of the few countries that performs some of its engineering work in the old British system units. Metric units are all based on fundamental physics quantities, which makes the metric joule, newton and watt much easier to use and calculate than the British BTU (British thermal unit), horse power, pound force and slug.
After the activity, students should be able to:
- Define and contrast energy, work and power.
- Given mass, distance, and time, calculate work, force and power using appropriate units.
- Given the conversion equations, convert between horsepower and kilowatts.
- Use measurement tools to apply the concepts of work, power and energy to a real life example.