Page:1

# TOPIC:

## C3-12 PENCIL AND PLYWOOD 10 years 2 weeks ago #25

 admin Topic Author Offline Administrator Posts: 189 Thank you received: 0 ID Code: C3-12 Purpose: Dramatically demonstrate inertia Description: A pencil is accelerated to almost the speed of sound by blasting it through a four-foot tube using a carbon dioxide fire extinguisher. The pencil will readily impale itself on a piece of 3/8" plywood. With a little bit of luck the pencil point will be virtually intact, although sometimes you need to re-sharpen it after the demonstration Availability: Available Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable. Please Log in to join the conversation. Last edit: by zzfixk21.

## C3-12 PENCIL AND PLYWOOD 8 years 6 months ago #1692

 lecdemhelp Offline User is blocked Posts: 65 Thank you received: 0 Some videos have recently been added to the demo page. To see the action in slow motion, click for 600 frame per second or 1200 frame per second version. Be sure to notice the vibration of the pencil after it is impaled in the plywood. Analysis of the 1200 fps video allows us to obtain an approximate value for the speed of the pencil as it emerges from the tube. The size of the plywood used in the demonstration was about 4 inches square; the length of the pencil is about 8 inches. A single frame shows the pencil traveling approximately 4 inches (10 cm) in 1/1200 second, or 12,000 cm per second, or 120 meters per second. This is greater than 1/3 of the speed of sound. A way to place a maximum limit on the speed of the pencil is to use the dynamics of the system. The length of the tube, along which the pencil is being accelerated is about 75 cm. Assume that the force on the pencil is equal to the vapor pressure of the CO2 acting on the area of the pencil to determine the velocity of the pencil at the end of the tube: v = SQRT(2 P A L /m ), where P is the vapor pressure, A is the inside area of the tube, L is the length of the tube, and m is the mass of the pencil. Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable. Please Log in to join the conversation.

## C3-12 PENCIL AND PLYWOOD 7 years 7 months ago #1714

 daetwyler Offline Administrator Posts: 83 Thank you received: 1 A neat video on another site of a related experiment: www.freshphotons.com/post/146668034970/r...is-looks-like-when-a Check this box to be notified of replies to this topic. Note: BBcode and smileys are still usable. Please Log in to join the conversation.
 Page:1
Time to create page: 0.095 seconds