EXPERIMENT MANUAL Franckh-Kosmos Verlags-GmbH & Co. KG, Pfizerstr. 5-7, 70184 Stuttgart, Germany +49 (0) 711 2191-0 www.kosmos.de Thames & Kosmos, 301 Friendship St., Providence, RI, 02903, USA 1-800-587-2872 www.thamesandkosmos.com Thames & Kosmos UK Ltd, Goudhurst, Kent, TN17 2QZ, United Kingdom 01580 212000 www.thamesandkosmos.co.uk
KIT CONTENTS What s inside your experiment kit: GOOD TO KNOW! If you are missing any parts, please contact Thames & Kosmos customer service. US: techsupport@thamesandkosmos.com UK: techsupport@thamesandkosmos.co.uk 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Checklist: Find Inspect Check off No. Description Qty. Item No. 1 Short anchor pin, blue 6 7344-W10-C2B 2 Anchor pin, red 15 7061-W10-C1R 3 Joint pin 4 1156-W10-A1R 4 Shaft plug 4 7026-W10-H1R 5 Shaft pin 1 7026-W10-J3D 6 Two-to-one converter 4 7061-W10-G1D 7 Tube, 80 mm 1 7337-W16-A1D 8 Tube, 30 mm 5 7400-W10-G1D 9 Washer 6 R12#3620 10 Nose piece 1 7402-W10-C2D 11 90-degree converter - X 2 7061-W10-J1D 12 90-degree converter - Y 2 7061-W10-J2D 13 3-hole wide rounded rod 2 7404-W10-C1G2 14 3-hole cross rod 4 7026-W10-X1D 15 5-hole rod 4 7413-W10-K2D 16 5-hole dual rod C 2 7026-W10-S3D 17 7-hole wide rounded rod 2 7404-W10-C2G2 18 7-hole flat rounded rod 2 7404-W10-C3G2 No. Description Qty. Item No. 19 11-hole rod 1 7413-W10-P1D 20 15-hole dual rod 1 7413-W10-H1D 21 Curved rod 12 7061-W10-V1G3 22 Square frame 2 7026-W10-T2S2 23 Large frame 1 7413-W10-J1S1 24 Curved frame 2 7392-W10-I1D 25 Motor axle 1 7026-W10-L1W 26 Axle, 30-mm 2 7413-W10-N1D 27 Small pulley 4 7344-W10-N3G 28 Rubber band, small 1 R10-02 29 Rubber band, large 3 R10-28 30 Large foam ball 3 K30#7366-2 31 Anchor pin lever 1 7061-W10-B1Y 32 13x3 Frame 2 7406-W10-A1D 33 3-hole bolt rod 2 7406-W10-B1G 34 5-hole L rod 2 7406-W10-B2G 35 Crossbow bolt 3 7406-W85-A-US 2
Catapults & Crossbows TABLE OF CONTENTS Safety Information... Inside front A Word to Parents... 1 Kit Contents... 2 Table of Contents... 3 Preparation... 5 Set up a target and learn about accuracy and precision. Classic crossbow... 6 Elasticity, potential energy, and kinetic energy Trebuchet one... 9 Vectors, speed, and velocity Scorpion...12 Gravity, acceleration, and air resistance Weighted catapult... 15 Mass, weight, and gravitational potential energy Reverse-draw crossbow... 17 Hooke s law Compound crossbow...20 Pulleys Trebuchet two...23 Levers and mechanical advantage Ballista...25 Projectile motion Catapult one...28 Kinetic energy, mass, and velocity Mangonel...30 Maximizing time in air0 2 4 6 8 10 12 14 16 18 20 Vertical distance (meters) y 10 8 6 4 2 0 Horizontal distance (meters) x 3
Catapults & Crossbows PREPARATION Setting up a target YOU WILL NEED metal pie pan or other durable dish tape measuring stick or tape measure Low accuracy and low precision HERE S HOW 1 Place a metal pie pan upside down on the floor. This is your bull s eye target. 2 Place a piece of tape 10 to 15 feet away from the pie pan. This is where you will stand when testing out your catapults and crossbows. WHAT S HAPPENING When you do the experiments with your crossbow, you should think about the accuracy and precision of where your bolts and projectiles land. Accuracy is how close your results (or shots) are to your target value in this case, the center of the target. Precision is how often you are able to get the same value, or have your projectile land in the same place. Look at the pictures to the right to see how accuracy and precision are related. Accuracy and precision are both critical concepts in the scientific world. Low accuracy and high precision High accuracy and low precision As you perform the experiments for each model, think about how the changes affect your precision and accuracy. Keep a record of your results for the different experiments. High accuracy and high precision 5
EXPERIMENT 6 Compound crossbow YOU WILL NEED 1 2 3 4 6 8 10 11 13 14 15 4 x 10 x 4 x 2 x 4 x 4 x 1 x 2 x 2 x 4 x 1 x 2 x 17 18 23 24 16 Background With the development of modern materials and manufacturing process, one of the most common changes in modern crossbows is the use of pulley systems. These crossbows are known as compound crossbows. The pulley system allows for the use of stiffer limbs which transfer more energy into the bolt instead of the movement of the limbs. 1 x 2 x 1 x 2 x 26 27 2 x 2 x 28 29 31 1 x 1 x 1 x 2 32 33 34 35 2 x 2 x 2 x 3 x 1 3 4 Side view 20
EXPERIMENT 6 12 13 Small rubber band 14 22 Large rubber band 15 Test out the crossbow by firing some bolts. Notice that when you load the bolt, the rubber band slides around the pulley. 16 Now try removing the pulleys and wrapping the rubber band around the peg. Do you notice any difference in behavior? WHAT S HAPPENING A pulley is a wheel on an axle which supports the movement of a cable or rope. The type of pulley used in this crossbow is called a fixed pulley. The fixed pulley is a two-armed lever that rotates around a fulcrum as it does work. Its load arm and lever arm are equally long in this case, so the user does not gain a mechanical advantage. However, this pulley is useful because it changes the direction that the force is applied. Looking at the rubber band you can see that the pulley allows the rubber band to be stretched farther, meaning that there is more energy in the rubber band. Application of force Lever arm Fulcrum Application of load Load arm