Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Scientific Frontiers Logo
TV Schedule
Alan Alda
For Educators
Previous Shows
Future Shows
Special Features

Dead Men's Tales
 
Teaching Guide
Activity 1 Splatter Spread
 
Activity
Answers
National Science
Standards and
Curriculum Links
Print version (PDF)
Main Menu
Help
 
ANSWERS

QUESTIONS

  1. Why were two plugs of potato needed for this cannon?
    (One plug sealed the muzzle end of the cylinder. The projectiles were placed atop of this "load" plug. The second plug was needed to seal the airtight chamber. This second plug was pushed into the cylinder and produced the increased air pressure needed to "pop" the load plug.)
  2. Would the cannon fire if the plugs did not form an airtight seal?
    (No. If the seals were not airtight, then the necessary pressure would not build within the cannon cylinder.)/li>
  3. How did the distance to the target affect the spread of projectiles?
    (The further the distance, the greater the circumference of the scatter pattern.)
  4. How does the friction between the "load" plug and the chamber wall affect the air blast?
    (If the friction is increased (i.e. if the dowel is pushed quickly),then the plug can withstand a greater pressure. With a greater pressure, the projectiles would be hurled a further distance. If the friction is reduced, then the load plug moves with very little pressure. Since an explosive pressure would not build within the chamber, the projectiles would slowly be pushed out of the pipe.)
  5. Why was it important to apply the same amount of pressure to the dowel during the two tests?
    (The diameter of the scatter would also be affected by the amount of friction, or the amount of pressure applied to the dowel. To try to eliminate this variable, the dowel should be pushed at a similar rate.)

Powder Burns
Unlike a shotgun or pistol can leave powder burns formed by the hot gases and materials that escape from the muzzle of the fired weapon. Explain how these burns might be used to infer the distance between weapon and victim.
(The nearer the target, the more likely the target will be peppered with the chemicals that are released during the discharge.)

return to show page

 

What Happened at Jamestown?Time TravelersA Texan Tall TaleThe Real Pyramid BuildersCity of Gold Teaching guide Science hotline video trailer Resources
Contact Search Homepage