Instructables

Golf Ball Catapult (HS Physics)

Picture of Golf Ball Catapult (HS Physics)
For our high school physics class at Verrado High School in Buckeye, Arizona, we made golf-ball catapults.
They are designed to send golf balls flying at insane speeds reaching up to or over 40 yards in distance.
Depending on your own construction, the catapult explained here was recorded to have an acceleration of 235 m/s/s, and could probably more if built more effectively then ours!

Construction is simple and requires only basic tools that are likely already somewhere around your house.

This took several days, but could be accomplished in a few hours, most likely, if you were dedicated enough and had all supplies ahead of time.
We did this mainly because of our study of motion and its related laws, including the law of gravity and Newton's Second Law.
 
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Step 1: Materials

Picture of Materials
To build this catapult, you will need some of the following materials. Keep in mind these can be variable depending on what you have available (i.e. arms to pivot on, drill sizes, etc).

Five 2-foot planks of wood(pref. 2x4)
Two 3-foot planks of wood(pref. 2x4)
Some form of pivot arm(can be vaired in width; must be over 2 feet long.
Wood or metal arm which can be used to throw golf-ball
Power-drill and drill bits
Golf ball
Metal braces
Screws
Two trampoline springs
Duct tape
Two 'circle' screws (i.e. pieces of metal which can be screwed into wood, the opposite end of which has a circular head which the springs can latch onto.) (See picture below if you don't understand.)
i was just wondering im doing this for a physics project but then we can only use rubber bands as our "spring" i was just wondering will this design work with rubber bands as the springs and if so around how far will it travel?
slashnano13 years ago
how does it work
Kiteman4 years ago
Are you sure about your data?

235 m/s is 2/3 the speed of sound.
faleure (author)  Kiteman4 years ago
As jschmadeke replied, we are sure of the data. Whether it is entirely accurate over time, is questionable. But initial acceleration is indeed 235 m/s/s
lemonie faleure4 years ago
You've confused acceleration with velocity. You should correct that.

L
that did confuse me.
Yep, 235m/s according to our triple axis accelerometer!  I saw the data :) 
Let me try this again.  This group's data was 235 m/s/s (if left off the other second in my comment above)

Don't confuse 235 m/s (speed) with 235 m/s/s (acceleration - change in speed over time, hence the second "s")

Students attached digital 25g and triple axis accelerometers to their catapult arms in a crude attempt to document the greatest acceleration of the arm.  The question posed to them was "What is the greatest change in speed over a said period of time?  Remember, acceleration can be negative and positive!

To find the velocity or speed of the arm, students would have to use our laser photogates to determine the time it took to travel a predetermined distance.  Since the class is an introductory course, I thought they could just investigate the acceleration aspect of the arm.

And... the greatest acceleration of the arm would be classified as negative acceleration - when the arm smacked it's stopping point (angle of release) and almost instantaneously stopped moving.  Kids may have confused it as being positive b/c of their perspective of the data being collected.

Here' s an example of some of the equipment and data collecting software they used:  http://www.vernier.com/pkgs/physics.html

Hope this helps ;)
Jonathan
http://www.aguafria.org/mrschmadeke  
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