Write down your results in a table similar to Table 1.If you notice that you are missing your target far to the left or to the right, it is fine to adjust the clamp and re-aim your catapult. Also, the catapult may move or wiggle slightly if you launch the ball really hard.But you can still count bounce-outs as a "hit." Note that, depending on the material of your target, the ball may be more likely to bounce out (for example, a hard metal pot instead of a softer cardboard shoebox).Are some settings more reliable than others? An easy way to measure this is to take ten shots at the target with the same settings and count how many hit the target. See if you can find different combinations of settings that enable you to hit the target. For example, should you make the pull-back angle bigger or smaller if that happens? If so, go back and pick another variable to explore. Maybe you find that your ball is always falling a few feet short of the target.For example, do you think adding more rubber bands will make the ball go farther or less far?.Go back to the Questions outlined in the Background tab, and try to use those to help you hit the target. Then you can experiment with different pull-back angles without changing anything else, and find out what pull-back angle works best to hit the target. For example: you could pick the orange ping pong ball, one rubber band, and a launch angle of 75 degrees.So, for starters it makes sense to keep three things the same and only change one thing at a time. However, if you start changing multiple things at once, you no longer have a fair test and your results may be too confusing to interpret. In this picture, the launch angle is 30 degrees.Īim for the target, and fire away! Remember there are four things you can change: the type of ball, the number of rubber bands, the launch angle, and the pull-back angle. Measure the launch angle by reading the tick mark that lines up with the bottom of the catapult base (on the right). In this picture, the pull-back angle is about 60 degrees. Measure the pull-back angle by reading the tick mark that lines up with the top of the launch arm (on the left). If you increase the number of rubber bands, what will happen to the launch distance?įigure 6.If you increase the pull-back angle, what will happen to the launch distance?.Which launch angle will cause the ball to travel farthest?.We have defined some of them for you in the Introduction, but you might need to look others up on your own. Terms and Conceptsīefore continuing with this project, make sure you understand the following terms and concepts. Think about how each of these things will change how the ball is launched, and which ones you will want to adjust to make the ball hit your target. The pull-back angle (from 0 to 120 degrees).The launch angle (from 0 to 75 degrees).The number of rubber bands (up to three). ![]() ![]() You can change four things to adjust how far the ball goes: The launch angle is the direction the ball is going when it leaves the catapult. ![]() The pull-back angle is how far back you pull the launch arm before you launch the ball. We will explain how to measure them in the Experimental Procedure.įigure 2. ![]() Figure 2 below can help you understand these angles. You set the launch angle by placing the pin through holes that line up on the disk and the base of the catapult. So, a launch angle of 90 degrees means the ball will go straight up, and a launch angle of 0 degrees means the ball will go horizontal. The launch angle is the direction the ball travels (relative to the ground) when it is launched. The pull-back angle is how far you pull the launch arm back before you launch the ball. The catapult is powered by rubber bands, which connect the launch arm to the "disk." The disk makes it easy to measure and set the launch angle and the pull-back angle. The ball (either a ping pong ball or a Wiffle® ball) sits in a cup at the end of the "launch arm," which is attached to the base. The base of the catapult, shown in Figure 1 above, is attached to a surface (such as the edge of a table) with a clamp. Note the paper towels between the surface of the table and the base of the catapult to avoid scratching the table. The catapult with all of its parts labeled.
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