Online Lesson Plan “Finding” Horsepower
Lesson Plan by who has taught science at both the middle school and high school levels for Lincoln Public Schools. She has written assessment and curriculum for LPS and has attained a Level II assessment certification. She has also served as a student teacher supervisor for the University of NebraskaLincoln.
Subject Area: Science 
Suggested Grade Level: Grades 68 
Learning Modality: Kinesthetic 
Multiple Intelligence: Logicalmathematical & Naturalist 
Bloom’s Taxonomy: Application 
What are these educational concepts? 
Objectives
In this lesson, students will:
 investigate horsepower as a unit of power;
 calculate horsepower from a set of given data;
 and look at history and discover that scientists and engineers of high achievement are considered to be among the most valued contributors to their culture.
Introduction
The engineer, James Watt, invented the term “horsepower.” Watt lived from 1736 to 1819 and is famous for his work on improving the steam engine. Watt was working with ponies lifting coal from a mine and wanted to devise a way to describe the amount of power they exerted. A Watt as a unit is used to measure all power whether it is mechanical or electrical.
Power is the rate of doing work. It is a measure of how quickly a job can be done. You can calculate power by dividing the work done by the time it takes to do it. The unit is footlbs/second.
Horsepower is a unit of power. Power has units of energy per unit time (P = W/t), and is measured in watts. One watt is one joule of work done in one second. The joule measures energy in physics in meters/kilogram/sec. And one horsepower equals about 746 watts. If you took a one horsepower horse and put it on a treadmill, it could power a generator and produce a continuous 746 watts.
One horsepower equals measuring how much power a horse could deliver.
Although one horsepower equals 746 watts, according to current engineers, a more reasonable number for a horse working an eighthour day is probably about 500 Watts. If Lance Armstrong (or another cyclist) could do 500 watts output power on a stationary bike, he would be considered strong as a horse! To help you understand the measurement, a bright light bulb draws about 100 watts, a microwave oven, 1000. A person uses food energy at an average rate of 100 watts.
The Resources
Links from within the Wessels Living History Farm site. [Note that clicking on these links will open a new browser window. Just close it and you’ll be back to this page.] Direct the students to these pages.
 Horses Finally Lose Their Jobs
 Tractor Innovations
 International Harvester Farmall Tractors
 AllisChalmers Tractors
 John Deere Tractors
 FordFerguson Tractors
 Case Tractors
Resources from outside Wessels. Direct students to these Web sites that are produced by others outside of the Wessels Living History Farm. [Again, clicking these links will open a new window.]
The Process
If you want to know the horsepower of an engine, a dynamometer is used. It places a load on the engine and measures the amount of power the engine can produce against the load. The tractor testing labs at the University of Nebraska tractor test site determined the maximum horsepower of the engines below.
If you plot the horsepower versus the rpm values for the engine, you get a horsepower curve for the engine. Peak horsepower for an engine is when the rpm value available form the engine is at its maximum. Torque is a measure of turning force, or said another way, a measure of how much a force acting on an object causes that object to rotate.
Dynamometers actually measure torque (in poundfeet). To convert torque to horsepower, you multiply torque by rpm and divide by 5,252. The number 5,252 is the result of lumping several different conversion factors together.
Using the information in the chart below, calculate the horsepower for each of the six tractors. Use the maximum number of revolutions per minute.
Type  RPM min.  RPM max.  Torque  Horsepower “hp” 
Allis 5650  1305  1850  123.6 lbft  
John Deere 5105  1402  1801  114 lbf  
Massey Ferguson 243  1248  1789  133 lbft  
Massey Ferguson 263  1321  1790  161.8 lbft  
Massey Ferguson 2220  1498  1800  169 lbft  
Case IH DX48  1602  2206  96 lbft 
Learning Advice
Other tractor data may be obtained from TractorData.com.
Teachers may wish to assign other problems solving for work or power from their classroom textbook.
Teachers could easily add this information to a physical science unit on work/power/watts and efficiency.
Conclusion of the Lesson
For nearly 200 years, the horse was the only supply of power on the farm. Until tractors were developed and used, the workhorse supplied the power to pull farm implements over every acre of soil planted. If farmers had to rely on horsepower to produce food today, our nation would need 20 times the number of existing horses, and five times the number of farm workers!
Assessment Activity
Tractor Type 
Horsepower (hp)

Weight (lbs)

Years Built

Cost

Case IH DX48  25  3,700  (unavailable)  (unavailable) 
J.I. Case SC  19  4,200  19401955  $1,700 
Case IH 9390  400  29,000  19971999  $160,000 
Allis Chalmers 8070  150  13,750  19821985  $60,000 
John Deere M  25  2,550  19471952  $1,075 
John Deere 5320  50  4,550  2000  (unavailable) 
Ford 2N  24  3,070  19421947  $1,120 
Ford 5900  50  5,760  19851993  $17,400 
Ferguson TE20  224  2,760  19461956  (unavailable) 
As you study the data from the horsepower chart, is there a correlation between the horsepower and the weight of the tractor? Is there a correlation between the weight and the cost of the tractor? Explain.
Can you estimate the cost for the missing data above based on the other information on the chart?
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