Our science studies have recently taken us into the field of physics, specifically trajectory. Trajectory is the path a free flying object (a projectile) follows through the air. A projectile has two forces working on it. The inertia that launches it into the air and the gravity that brings it back down to earth.
So how do you study trajectory? By hurling things into the air!
DIY Wooden Catapults
I found a great post at Housing a Forest showing how to make simple catapults and I knew we had to give them a try in our science lesson.
My husband took the wood we used for our lever experiments and cut it down to make catapults. He made a variety of sizes so we could see if the size of the catapult made a difference to the trajectory. Some had a longer arm and others had a slightly thicker base.
Hands-On Science Experiment
First everyone chose a small stuffed animal to launch. The kids put their animal on and stepped down on the other end. None of the animals traveled too far.
They decided to try again, this time increasing the force, by stepping harder. Some of animals moved further, especially for the bigger kids. One of the kids stepped so hard, he broke his in two!
On the final attempt, the kids jumped or stepped onto their end of the catapult as hard as they could. This did send the animals the highest they had been, but it was still less than what everyone was expecting.
What we learned
Trajectory is only changed by two things; the speed at which you launch the projectile and its angle during launch. When you increase or decrease the speed or angle during takeoff, the trajectory of the projectile will change.
Even though we had varied the catapult sizes slightly, there wasn’t really enough difference between them to launch the objects we had chosen off into higher trajectories.
By increasing the speed at which they were launched (by stepping on the board harder) some kids were able to lengthen the distance they flew. If we had also increased the angle of the wood, we probably would have seen a bigger difference in the path.
Since we couldn’t change the angle of the catapult, we decided to try it with a lighter object, a marshmallow. The kids followed the same steps as before, but had much better results. The decreased weight of the projectile was a much better match for the catapults we had.
We just love bringing science to life. It’s one of the reasons we’ve all enjoyed using the Disney Imagineering Videos so much.