Physics of Catapulting

1
Physics of Catapulting

• By
• Andrea Kuchta

2
Catapults

• Defensive and offensive weapons that were used in
  medieval and primeval warfare before artillery
  was invented
• Forerunner of guns
• Launch projectiles long distances

3
Items used

• 1 Ping- pong ball
• 1 Plastic spoon
• 1 elastic (rubber band)
• 1 Paper cup
• Scotch tape
• Coins
• 1 Small (full) plastic bottle
• 1 small, perfectly round stick of wood

4
Making A Homemade Catapult

1. Put 2 aligned holes in the sides of the cup
2. Be sure they are big enough for the stick (which
   acts as an axel) to spin freely in
3. Put change in the cup to weigh it down
4. Using tape connect the spoon to the stick
5. Tape the small bottle to the cup between and
   perpendicular to the holes
6. Tape the elastic to the top of the small bottle
7. Using tape connect the elastic to the spoon so it
   stays put
8. Place the small piece of wood in the holes

5
The experiment

1. Place the ping-pong ball on the spoon
2. Pull back spoon
3. Record the angle and release
4. Mark the landing point and measure the horizontal
   distance
5. Repeat steps 1-4 two more times
6. Place data in data table

6
What Happened

• As I increased the angle of the spoon
• The tension in the elastic increased
• Increased the force
• The ping-pong ball gained more potential energy
• When released
• Potential Energy in the ball was converted to
  Kinetic Energy
• The force created by the tension gave the ball
  even more energy

7
The Physics Behind It

• The further you pull the lever back the more
  tension you are creating in the elastic
• As you pull the spoon back you are increasing
  its angle
• increases the tension in the elastic
• The tension in the elastic creates a force which
  acts upon the ping-pong ball when it is launched
• The more tension you create the more energy the
  ball will be given
• Tension and force are equally proportional
• Meaning the greater the tension is the greater
  force acting on the ping-pong ball will be
• The force exerted on the ball gives the ball
  energy

8
The Physics Behind It (continued)

• As you pull the spoon back the ping-pong ball
  gains potential energy which is converted to
  kinetic energy when released
• The angle and horizontal distance are equally
  proportional
• The greater the angle you launch it at the
  farther it will travel in the horizontal direction

9
Bibliography

• Works Cited
• Dolores Gende Ap Physics Catapult Project. 7
  Feb. 2007 lthttp//apphysicsb.homestead.com/?catapu
  lt.htmlgt.
• Faughn, Jerry S., and Raymond A. Serway. College
  Physics. 6th ed. Toronto, Ontario, Canada
  Thomson, 2003.
• Gurstelle, William. The art of the catapult
  build Greek ballistae, Roman onagers, English
  trebuchets, and more ancient artillery. Chicago,
  Illinois Chicago Review, 2004.
• How does a catapult work? How Stuff Works. 7
  Feb. 2007 lthttp//www.howstuffworks.com/?question1
  27.htmgt.
• Radlinski, Filip. Principles of motion. How
  Stuff Works. 7 Feb. 2007 lthttp//www.howstuffwork
  s.com/?framed.htm?parentquestion127.htmurlhttp
  //www.geocities.com/?SiliconValley/?Park/?6461/?tr
  ebuch.htmlgt.