Fire away

Proof of Efficacy Document

Our task was to create a trebuchet to launch a projectile. The assignment was to launch the projectile as far as we could we created one which worked, but not as well as we would have liked so we went back to the drawing board to make modifications

Our machine consisted of:

Two legs
A base
An axle
An arm with a screw on bottom to attach rubber bands
A counter weight to increase velocity
A hook in base to attach the rubber bands

Our original design worked, but it didn't go very far our group waas reaching ten meters while some other groups were reaching 40 meters. So we went back to the drawing board and made some modifications.

Arm ratio 1.5 to 1 which caused. weight balance so all energy goes to projectile not the arm.
Number of rubber bands. It is more Pe to Ke
Longer arm. More distance in same time = gain in velocity
Counter weight. PE= mgh more m more PE
Longer and skinny projectile. less air resistance
Lighter arm. Force= mass times accelration.
More pull back distance. More Pe to Ke 1/2 kx squared more Ke
No stopper. Allow PE to convert to KE in follow through

Our trebuchet has been started from the ground up without a sturdy base; everything else will be weak. That's why we picked out a heavy strong sturdy piece of wood. Then we selected two 2x4 legs that would be sturdy and would not move around. We also considered to height we wanted it to be taller to accumulate the long arm. Next we grab a piece of wood for an arm we found the ratio for the arm we also added a counter weight and more holes in the arm to make it lighter.

Calculations:

Projectile mass: 17 g

Horizontal distance 13 meters

Time in air 1.78 seconds

Vertical distance 15.5 meters

Horizontal velocity 8.7 m/s

Vertical Velocity 17.4 m/s

Total velocity 19.4 m/s

Angle of release 64 degrees

Spring constant 50 newtons per meter

initial spring potential energy 6.75N

Kinetic energy of the ball 33.7 KGM/S

percent converted from Pe to Ke 51% conversion

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