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U.S. Navy Museum Cold War Gallery Lesson Plan
Newton's 2nd Law Revisited: Sea vs. Air, Fast Attack Submarine vs. Airborne Laser
Developed by Bill Sanford, Nansemond Suffolk Academy, Suffolk, VA
2012 Naval Historical Foundation STEM-H Teacher Fellowship
 

 
  Instructional Goal

Teacher Help
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Review and Practice Calculations Involving:
  • Metric / British Conversion
  • Kinematics
  • Newton's Second Law
  • Non-Conservative Forces
  • Energy and Power
NOTE: This is an algebra based lesson plan, but the problems could easily be adjusted to challenge students familiar with calculus-based physics. It covers material from multiple chapters, such that it could be used as an end of term review activity, or broken up and used throughout the year as the concepts were covered.

Background

What is Better Than the Army Navy Game?!?!?! How about Navy vs. Air Force, Sea vs. Land. Los Angeles Class Submarines were instrumental in establishing our strategic dominance during the Cold War. The Airborne Laser represents the Star Wars technology envisioned during the Reagan years.
  • Which has the more powerful propulsion system?
  • Does one speeds-up more quickly than the other? ...why?
Resources:  None

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Lesson Activity

Objective:

Review and Practice calculations involving Conversions, Kinematics, Newton's Second Law, Energy, Non-Conservative Forces and Power.

Materials:

Activity worksheet: Click Here

Instructions:

Today we compare a Navy Los Angeles (688) class Submarine with the Air Force Airborne Laser (a Boeing 747 airliner). Thoughts to ponder...
  • Which has the more powerful propulsion system?
  • Does one speed up more quickly than the other? ...why?
688 Class Submarine Air Force Airborne Laser (Boeing 747)

688 Class Submarine
  • Los Angeles (688) Class Submarines were designed as Fast-Attack submarines because their main purpose was to hunt down and kill other submarines. Among other things, they needed to be able to accelerate quickly to evade enemy torpedoes.
  • They were also designed to be able to keep up with fast moving Aircraft Carrier Battle Groups, so they could sprint out in front of the carrier and make sure the path was clear of enemy ships and submarines.
  • mass = 7.00 million kg
  • Shaft horsepower = 34850 hp or 26 MW
  • Speeds up from 0 to 20.0 knots in one minute
Air Force Airborne Laser (Boeing 747) (program cancelled in 2010)
  • Aims a basketball width laser beam, able to destroy a large incoming missile.
  • Weight = 875,000lbs
  • 4 engines
  • Each engine generates 432,300 horsepower
  • Speeds up from 0 to 175mi/hr (290km/hr) in 30.0sec

Show your work for conversions and calculations used to complete the table in the Activity Worksheet. You will need to make conversion factors out of many of these helpful conversion equalities. There are others that you will need, but you should have memorized them by now, or you can look them up.

1 knot = 1.151 miles per hour 1 m = 3.281 feet      1mi = 5280 ft
1 horsepower (hp) = 746 Watts 1 pound (lb) = 4.45 Newton

Activity Exercises:
  1. Assume that the acceleration is constant during these problems.
  2. Use the speeds and the time to calculate the acceleration.
  3. Using the acceleration and the vehicle's mass, calculate the net horizontal force exerted during this time period.
  4. Calculate the power of the propulsion plant (for the 747, the power for all 4 engines combined).
  5. Using Kinematics, calculate the distance travelled during the period of acceleration.
  6. Using the rated power of the vehicle's propulsion plant, calculate the amount of energy wasted...expended by the propulsion system, but not converted into kinetic energy of the vehicle.
  7. Using the wasted energy and the distance, calculate the average fluid friction force experienced during the period of acceleration. How does this force compare with the weight of the vehicle?
  8. Calculate the factor by which the airliner value compares to the 688 value, e.g. mass(plane)/mass(sub)
 
 

 

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