Water Bottle Rocket Engineering

The picture on the left is of our rocket. It is made out of two 2L bottles, although we cut off a fourth of one in order to elongate our rocket without making it too long. As you can see, we fit the bottle without the bottom onto the other bottle so they overlapped a bit. We made four fins out of cardboard and taped them with scotch tape to keep them waterproof. We then glued the fins to the bottom of our rocket as well as taping them, to make sure they didn't fall off our break off when the rocket landed. Our cone was made out of a lot of paper which Rachel and I folded into a cone shape and then taped it up as well. Not only that, but in order to add a little extra weight to the top of the rocket to keep it from getting out of control, we taped a rock to the inside of the top of the cone. We also made a parachute out of a trash bag. We connected the parachute to the bottle by poking four holes into the parachute, then threading string through them. 

While launching the rocket today, we didn't use the cone, since we hadn't yet finished the parachute and only had thirty minutes left for launching practice. Our rocket, surprisingly enough, did a lot better than Rachel and I expected it to, since we didn't actually have any added weight on the top of the rocket to make it steadier. However, both times we launched the rocket, it was in the air a little over six seconds both times. We filled the rocket about halfway with water, and pumped it to around sixty psi. While the rocket did wobble a bit while in the air, it went really high, so hopefully we can fix it by adding more weight to the top of the rocket. 

Hopefully tomorrow after testing the rocket with the parachute and making adjustments it manages to stay in the air for at least ten seconds. While I'm still really worried, I think that with the two hours we have for launching the rockets, Rachel and I will manage to do whatever we need to do to get our rocket to stay in the air for those four extra seconds.

Physics Unit 8 (Part 2)

Today we learned all about power. Power, is the rate at which work is done, and work, in case any of you have forgotten, is the change in energy. To find power, you take an objects work and divide it by the amount of time used. The unit used to measure power is watts.

Power = work ÷ time
Work = newtons x meters

We had a lab today where we had two students run up stairs. We then recorded their masses, the distance up the stairs they travelled and the amount of time it took them to get up all the stairs. With that information, we were able to find the students' forces, which then allowed us to find their work as well as their power.

In the picture to the left, my dog is running down some stairs. Let's say she has a mass of 8kg, ran down 1 meter of stairs which took her 2 seconds, and that she's on Earth (which she is), so gravity would be 9.8ms^2. This means that she had a force of 78.4N (force = ma). Now that we have her force, we can find her work, which would be 78.4J (work = Nm). Finally, we can find her power, which would be 39.2W (power = work/time). If Abby was a Great Dane, she would have a much higher power, because when object's have greater masses, they have greater powers.



We also learned how to draw energy graphes, which is actually really confusing at times. The graphs, no matter how confusing they are, are actually really good at demonstrating the concept of potential energy vs. kinetic energy. Through time, as the potential energy went down, the kinetic energy got higher, which was made clear in the graphs. The same thing works for other concepts too, like kinetic energy vs. work.

Physics Unit 8

In class, we learned about energy and work. We learned about the different types of energies and how to find them. We also learned about the Law of Conservation of Energy, which states that energy cannot be created or destroyed, it only changes form. Energy is a scalar quantity, which means his has magnitude but no direction. We also learned about joules, which is the unit you would use for energy, and is found by multiplying the object's force (newtons) with its height (meters).

There are three types of energy (that we learned about):

Kinetic energy = energy of motion. Temperature is a measure of average kinetic energy.
Its equation is KE = 1/2 x mass x (velocity)^2 = 1/2mv^2.
The picture on the left is my Jack Russell Terrier, Abby. So, using the equation, if she had a mass 8kg, and a velocity of 2m/s, her kinetic energy would be 16 Joules.













Spring potential energy = the potential energy in a spring (its name speaks for itself). Its equation is PEs = 1/2 x spring constant x (the distance the spring is stretched/compressed)^2 = 1/2kd^2. In order to find the spring constant, you would use the slope of a Force vs. Time graph.  The picture on the left is of a rubberband and a spring, both of which have spring potential energy when they are either stretched or compressed.

Potential (gravitational) energy = the potential energy of an object (once again, it's name speaks for itself). Its equation is PEg = mass x (acceleration of) gravity x change in height = mgh. The picture on the left is of my deodorant                   (ew, deodorant) about to jump off my dresser, which is about a meter tall. If my deodorant has a mass of 1kg, and yes, we are on Earth, then my deodorant's potential gravitational energy is 9.8 Joules.











Some extra equations we learned are:
Hooke's Law = Force of spring = -kd. K is the spring constant, and d is the distance that it is stretched or compressed. The negative in front of the k is to show which direction the spring is being pulled/pushed. This equation doesn't actually have to do with energy, but is still useful.
Work = change in energy = force x distance.

Egg Drop Lab

 Caitlin and I made our capsule out of a cardboard box. Since we the biggest our box could be was 35cm x 35cm, we made ours with a height of 31cm, a width of 16cm,  and a length of 31cm as well. We used a golf club sock and stuffed crumpled paper halfway into the sock to provide cushioning, as well as to crumple upon impact when hitting the ground so the time of impact would be elongated. This would allow the average force to be spread out through a longer period of time, so all of the force didn't act upon the egg at once. When putting the egg into the sock, we put bubble wrap around it as well, so there was a lesser chance of the egg moving out of place and cracking. We also wrapped the sock in bubble wrap for the exact same reasons. Caitlin and I also put a lot of crumpled paper into the box around the sock and under it. When we were brainstorming how to make the capsule, Caitlin and I thought it would be a good idea to accordion fold the sides of the box so they could crumple as well upon impact, but then we just decided not to. Lastly, we made sure our box was light, so there wouldn't be as much force when the capsule was dropped.




As you can see in the picture to the left, there are two diagrams. The first shows the capsule when it's falling. The forces that are acting upon the capsule are air resistance and weight, air resistance pushing up, and weight pushing down. The reason air resistance is so much smaller than weight, is because, since the capsule is falling, weight has a stronger force than air resistance does. The second diagram is for when the capsule hit the ground. While the capsule was still accelerating downward, its normal force was so much bigger, since it had just hit the ground, which is shown in the diagram.

Our capsule was 100% successful! The reasons for its beautifully untarnished shell, was mostly because of all the padding we had in the box. All the paper and bubble wrap lengthened the contact time, which, as I explained earlier, meant that there was less average force per second, so the force acted upon the egg at a much slower pace than if there was no padding at all. Also, as you can see of our capsule in the top left picture, it looks like our capsule hit the ground on its corner, which was the optimal area, since that corner was the farthest away from the egg, which was in the middle of the box. I think if I were to do this lab again, I would try to make the capsule smaller than it was before, since the less mass it would have, the less force there would be when the capsule hit the ground.

Physics Unit 7 (Part 2)

Today, we reviewed momentum and impulse more. The picture to the left is one of the examples that were demonstrated in class. Someone would be sitting on the hover board while another would be sitting on the danger board. They threw a medicine ball between them, and when they did, both the person throwing the ball and the person catching the ball moved backwards. The reason thrower's moving back was because as they exerted force onto the ball, the ball was exerting the same amount of force onto them, which caused them to accelerate backwards. As for the catcher, when catching the ball its momentum was transferred to the catcher, since momentum is conserved. In the situations, one person moved farther back than the other (normally it was the person on the hover board, but that could've been because the danger board had friction) and this is because they had less mass than the other, so they had a higher velocity.




The only new thing I remember learning today is the rule that under the curve of a Force vs. Time graph, the area is equal to impulse. Speaking of impulse, we went over it a lot today and I still find it incredibly confusing, so I thought I would just write out the equations/definitions as a review for myself and whoever else wants it.

Impulse: the average force exerted upon an object multiplied by the time the force is acting on the object. Change in momentum of an object.

Impulse = J or I ('cause it's just cool like that)

J = change in momentum = mv - mvo = avg. force • change in time

Physics Unit 7

Today we started Unit 7 (woohoo!!) which is based on momentum and collisions. We spent the day learning about momentum and and impulses. Momentum, whose variable is p (capital P is for total momentum), is a vector quantity, which means it can be added like vectors. To find momentum, you would do mass times velocity. And in order to find the total momentum, all you have to do is add up the individual momentums. The Law of Conservation of Momentum states that in a closed system, the momentum of a system is always conserved. Impulse is the average force upon an object multiplied by the time the force is acting on the object. Impulse is also the change in momentum of an object, and its variables are I and J (totally makes sense, I know).

In case my explanations were confusing and you would have preferred equations, here they are:
p = momentum
P = final momentum
I or J = impulse

F = force
p = mv
P = p1+p2+p3...
I = F • change in time
I = change in momentum = mv - mvo

In today's lab, we used air tracks and used two gliders to measure their collisions and see how their velocities changed based on their masses and how they hit each other. We used rubberbands at first so that when the gliders hit, they would bounce off each other. This kind of collision is called an elastic collision. We also replaced the rubberbands with two metal pieces, one side with a pin and the other with wax, so when they collided, they would stick together rather than bounce apart. This kind of collision is called an inelastic/sticky collision.

Also, we could all use a little Bill Nye in our lives, so here is a video where demonstrates aspects of physics, if anyone wants to take a walk down memory lane (I was going to just add the whole episode link, but it didn't work).

Physics Semester 1 Review

Uugh, I can't believe that the first semester is already over and that it's only been three weeks. It feels as though we have spent months in this class and yet hardly any time at all. That's probably because we learned so much these past three weeks.

In Unit 1, we learned about accuracy and precision, conversions/stoichiometry, scientific notation, and the different types of graphs. We mostly focused on the graphs and the different relationships their variables have with each other, which was helpful, since we're still using that knowledge now while making graphs.

In Unit 2, we began learning about kinematics. We learned about motion maps and how to draw them, and about scalar and vector quantities. We also learned about the difference between distance and displacement, speed and velocity, what acceleration is, as well as about the three graphing rules.

In Unit 3, we learned more about acceleration. We learned how to draw Distance vs. Time graphs, Velocity vs. Time graphs, Acceleration vs. Time graphs, as well as how one graph could help us draw another one. We also learned about the DAT, VAT, and VAD equations and how to use them, as well as what steps to take while solving the equations.

In Unit 4, we learned about projectiles. We learned about how to draw diagrams of projectiles and how to draw graphs. We also learned that when making graphs, the two axes are independent. We also learned how to use the DAT, VAT, and VAD equations to find whatever factors we needed. These problems were complicated at first, but became a lot easier with practice.

In Unit 5, we learned all about forces in equilibrium and how to use vectors. We learned the bureku technique, which allows us to break up diagonals on free body diagrams in order to find the information we need. We also learned what force is, which is a push or pull and is a vector quantity, as well as a couple types of force. Lastly, we learned Newton's three laws of physics, which provide us with a greater understanding of why things act the way they do.

In Unit 6, we focused on Newton's second law, which states that Fnet=ma. We learned how to draw and do problems that involve acceleration, which we didn't know how to do in the previous lesson. We also learned more about friction, and how there are two different types: static and kinetic. Static friction is stationary motion, while kinetic friction is moving friction. We also learned how to find the force of friction, which is equal to the coefficient of friction times the normal force. The coefficient of friction is pretty much based on the stickiness of the object.


In all honesty, I absolutely love this class! Mr. Blake makes learning interesting by adding in jokes and relating to us, unlike other teachers, who would just talk at us without waiting to see if we understand. I think the pace of this class is almost perfect, if not a little fast sometimes, but I don't really think there's any way that can be fixed, since we have so much to cover in so little time. I also like how I am beginning to look at things outside of class and being able to relate what they are doing to what we are learning in physics.

Most of the stuff we learned I understand decently, but units 5 and 6 are definitely the two units that I struggled the most with. I have a hard time doing the bureku technique as well as drawing free body diagrams, since I find them so confusing. However, the reason that I have such a hard time with units 5 and 6 could just be because we only learned them this week, and we didn't have enough time to practice. Either way, I'm really looking forward to another fun 3 weeks of physics!!