Concepts

Projectile motion

Overview

A monkey (held by an electromagnet) in a "tree" will fall when startled by blowgun fire (which breaks a wire to cut off the electromagnet current). The question for students is this: where should the gun be pointed to strike the monkey? Should it be aimed above, below, or straight at the monkey? Answer: straight at the monkey.

Details

Equipment

• [1] Mounted blowgun
  
• [1] Bullet
• [1] Mounted electromagnet
  
• [1] Mounting pole
• [1] Pole clamp
• [2] Wooden block
  
• [1] Current supply
• [2] Banana cable
• [1] Monkey or can
• [1] Lifter pole for monkey or can
• [1] Foam
• [1] Extension cord
• [1] Long double banana cable
  
• [1] Stick
• [1] Ethanol bottle
• [1] Box of wipes
• [1] Metal cart

Classroom Assembly

1. Sanitize the blowpipe with ethanol and a wipe.
2. Mount the electromagnet on the cart using the mounting pole, clamp, and wooden blocks.
   
3. Connect the electromagnet to the blowpipe with strain-relieved cables.
4. Connect wire across the blowpipe exit.
   
5. Plug in and set the current supply to the appropriate output (monkey: 0.5 A; can: 1.5 A).
6. Set switch to "off" position.
7. Lay down the foam under the electromagnet.
   
8. Test magnet's ability to hold monkey/can.
9. Turn off the current.
   
10. Check the aim of the blowpipe.
11. Lock the wheels on the cart.
    

Important Notes

• Practicing this demo before class is highly recommended.
• Make sure no one is in the line of fire should the bullet miss or riccochet.
  
• Remember to turn off current to the electromagnet when not in use. The magnet can get very hot.
• Moderately good breathing strength is required to operate the blowgun.
• The bullets are very easy to lose. Please try to recover them after firing.
  
• When attaching the thin wire to the blowpipe, make sure to loop the wire around the holder at least once on each side.
• The stick is to push a bullet out of the tube in case it gets stuck.

Script

1. Double-check the aim of the blowpipe.
2. Insert the bullet.
3. Turn on the current.
   
4. Take a deep breath and blow out the bullet.
5. Turn off the current.
6. Find the bullet.

Additional Resources