Water Bottle Rocket Preview

Today, we did practice launches with our water bottle rockets. We created a more elaborate version of our water bottle rocket and we also created parachutes made out of trash bags. For our rocket, we cut the top off of a 2 liter soda bottle and attached it to the bottom of the complete bottle. We added cardboard fins to help the aerodynamic aspect of the launch, and we attached 20g weights to the bottom of our rocket to ensure that it would fly right side up. For our parachute, we used a whole trash bag. We cut slits to create the four corners of the parachute and made loops at the end in which to attach the parachute to the rocket using thin rope. Capping the rocket with a cone at the launch helped with the aero dynamicity of it and once it started to descend, the cone flew off and the parachute deployed. It was really cool to watch our simple machine fly so far up in the air and come floating down.

Unit 8 cont.

Today in class we started practice launching for our water bottle rocket lab. We filled our water bottle rocket past half way then used a special pump to pump air into the bottle until the pressure was up to 50. We then pulled the plug from the lip and it flew up into the air. If you looked at this lab in a physics perspective, we were increasing the potential energy of the "rocket" by pumping air into it. Once we significantly increased the potential energy of the rocket, we released the plug and the rocket shot up, increasing its kinetic energy and decreasing its potential energy simultaneously. This got me thinking about the wind up toys I loved so much when I was little. If you think about it, its very similar. The more you wind up the toy, the more you are increasing its potential energy. And though the release of that potential energy (become kinetic energy) is less dramatic, it has the same effect on the wind up toy as the water bottle rocket.

Unit 8

Today in class we started a new unit about Energy & Work. This unit was especially interesting because many parts of the concept of "work" go against your intuition. If you were trying to push a heavy object, you would think you would be putting in a lot of work because you are putting in a lot of effort. Yet if the object isn’t budging, then regardless of how hard you try, there is zero work involved. (in Physics terms) Furthermore, if you are spinning around but are staying in the same position, then your work is also zero, regardless of how many times you spin around. This amazed me and got me thinking about figure skating. Back in Japan, I used to love this figure skater named Shizuka Arakawa.

(pictured below) Though she may be spinning endlessly, she is putting zero work in.

Egg Drop

The idea behind our egg drop container was to have something that was small to reduce bouncing around inside the container, padded to hopefully prevent cracking from the impact when it landed, and light so it would reach maximum velocity relatively quickly. In our small air tight tupperware container, we packed as much stuffing as would fit in order to cushion the egg. After sealing it tight, we taped spongey pieces of foam around the tupperware to break the fall and extend the contact time.

As you can see in our diagram, there was weight force pulling the egg down, normal (contact) force pushing the egg up, and air resistance also pushing the egg container up on its way down.

Despite all of our efforts, the egg didn't survive the drop. I think we focused too much on making the container light rather than spending our time trying to figure out how to decrease the impact on the egg. We should have added more padding and made the container more air resistance so that the terminal velocity would be slower than gravity.

Unit 7 cont.

In today's lesson, we learnt about momentum. Our labs and activities were focused on the Law of Conservation of Momentum – In an isolated system, momentum will be conserved. This means that momentum will be transferred between objects in order to be "conserved" and saved. So tonight when the fireworks were going off, it got me thinking about momentum. Because there is no additional fuel to be burned after the initial takeoff, all the movement you see in a firework is due to momentum. After the first burst of force, the firework will continue to move up with momentum, fighting the force of gravity acting against it. It amazed me to think that momentum could solely push the fireworks hundreds of feet upward against the force of gravity.

Unit 7

Today's lesson in class was based on a new unit – Momentum. It incorporated the previous unit on force, as force is one of the variables in the equations that solve for momentum. We did a lab activity that involved pushing two carts toward each other with a bouncing mechanism on a frictionless surface. During this lab, I observed that the faster one cart was going, the more force transferred to the slower cart, leaving the initially fast car move really slow. This reminded me of the action movies I love so much. The overly dramatized fighting scenes often show two people running toward each other in order to fight. One person runs at a higher velocity, and it is the person that is running faster that transfers his force to his opponent. This person staggers back a couple steps while the opponent goes flying out of the screen.

Summary of Quarter 2

Units 4 through 6 were focused more on motion in the real world, situations we encounter in our every day lives. In Unit 4 we learned about projectile motion, which is motion in the horizontal direction as well as the vertical direction simultaneously. In Unit 5, we learned about forces in equilibrium, which are the forces acting upon objects that are either stationary or moving at a constant velocity. In the next unit, Unit 6, we furthered our learning about forces, but this time we learned about forces that accelerate. (Newton's 2^nd Law of motion) This was more complicated than the last unit because this time we were learning about the forces acting upon objects that are accelerating. These three units collectively have helped me to understand motion in a real-world, practical way.