Plastic tack car demolition derby!

Hey, nothing better than being told you can roll things into each other, right? Unless your me and accidentally cause the funniest moment of the class when you discover that there springs on each of the cars that can be pushed in and hidden and popped out at the press of a button. ;)

This lab was all elastic and inelastic collisions, with equal and different weights. We did 16 total tests, 8 inelastic. For the elastic "collisions" there were magnets in the carts facing each other. Opposite charges came together so the carts bounced away as they got close. For the inelastic tests, velco, so that the carts would lock.

So lets just establish right now. Whenever heavy cart met light car (the heavy cart would have a mass three times more than the light cart) heavy cart won, and it often resultd in light cart going flying the other direction, unless it was going the same direction as the heavy cart, in which case their momentum would end up becoming one between the two of them.

When the carts were the same mass, they would exchange their momentum which was much closer to the same. When the exchange happened between heavy cart and light cart, one cart almost always slowed dramatically.

Circly, Mathy stuff!

Well, this was another one I wasn't expecting. Spending a class analyzing circles. And then reporting out findings on a slope of a graph involving Diameter vs. Circumference. All done by hand. This meant measuring around the outside of each object for the circumference, using tools to measure the diameter, and outlining the object on a grid to then attempt to calculate area.

After the calculating, it was time to go to the infamous whiteboards, to create a graph with one set of data. We may have had an outlier on that graph, but then again, we may have also cheated when it came to getting data for a hula hoop because that was going to be a nightmare to measure. So it was to the internet for the hula hoop data. But using the data we got for diameter and circumference, we were able to make a graph with a slope based on 6 items we measured and the hula hoop.

Cartoons are real...they just use fake physics.

Ok, I can honestly say, when I signed up for physics class, I never imagined that part of the class would be cartoons. Like, really? I am going to go to class to...watch cartoons??? But there is more to it than that. We must laugh at the comedy show that is cartoon physics. Unless of course a coyote can push a boulder which appears to be more than twice the size of himself down a ledge, across a road, back of a cliff on the other side which is taller than the ledge, and when all is said and done, have a boulder on top of himself.

Once again, laugh away at the cartoon physics because that shouldn't be physically possible. But it does make an interesting conversation, and lead to a lab involving attempting to figure out just how high you would need to release a ball from to get it to go in a loop, where you then use mgh=PE to figure out the potential energy needed to create such a phenomena.

But lets look for a moment at the energy. The boulder starts with all potential energy, and ends with all potential energy once it lands on top of the coyote. But at the base of the canyon it would be all kinetic energy, since there is no way it can gain any more energy (and yet it magically does) and as the boulder goes up the cliff and is in the air, it has both.

Back to our experiment. Based on what the cartoon showed, you should be able to release a ball at half the height of something and have it go in a loop. That is illogical though, because the object needs to have enough energy to go up the other side. So we did a mini version of this to see what the minimum height to get a ball to go in a loop would be. We got our ball to go around at a height of 14in. or ..228m in extra height, with the ball weighing 9.2g. mgh=PE made PE=20.5564

Why must there be unbalanced forces!?! We don't need to move in our lifetimes!

What are unbalanced forces. Well, a person skydiving is an unbalanced force. That is, the force of gravity is acting straight down on them, but nothing is acting up so they are plummeting down towards earth. The forces acting on that person are unbalanced.

In other words, balanced forces = equilibrium = stationary objects, unbalanced forces = some form of motion as the balances are unable to keep each other in check.

One small step for mankind, one large...crash??? For eggmanity???

Yeah, not my finest work. Stay up late and wake up early designing a parachute, just to release it wrong and have the chute not open. But even though the design had a fatal flaw in that if the chute didn't start open it wouldn't open, the work that went into the multiple designs was there.

It also doesn't ignore the fact that since I didn't get the air resistance I needed to create a nice, relaxing flight for my egg, my parachute accelerated all the way to the bitter end. That left me wishing I had gotten a video of the failed flight for two reasons.

1) There is nothing like watching an egg smash against the floor of the school and not getting in trouble for it and;
2) I could have looked at the video more closely and figured out how fast my egg plummeted to the ground at by calculating how long it took, how heavy it was, and breaking that down into chunks (m/s/s).

Now if only I hadn't had my little mini-chute. Then it really would have fell in a hurry.

Anyways, I mentioned 3 designs. Well, I have already referenced my initial design. My "mini-chute." A cute little chute that probably couldn't hold my than a couple cherry tomatoes, just because it didn't have enough surface area. So I moved to my second design. A larger square parachute. The problem with this, it there was no real way to make it stay open and not fold in on itself. So I went to pan three (all made up as I went). My little mini-chute underneath a mushroom-top larger parachute. This design showed some promise and I was running out of time and materials, so I decided that I would except design #3 as my final test design.

Needless to say, it didn't go as I hoped. But the experimental design phase was there, and it was as thought out as can be for 1am and 5am. :)

Force diagrams, Balanced Force and equilibrium? Same difference

So in my last post I explained balanced force as anything that had equal forces so that it wasn't moving. That can be called being in a state of equilibrium.

So take this for an example. You place an apple on the table and it stays perfectly still. First off, what forces are acting on the apple? The table is acting straight up, and the force of gravity is acting straight down. You can draw that out to be a force diagram. That is a diagram which is used to visually represent every force that is acting on an object.

But back to the apple, it is perfectly still. That means that to force put on the apple by the table and the force put on the apple by gravity are equal. That apple is in a state of equilibrium. This literally means that it is balanced.

Balanced forces make my life easy. Thank you Newton

Life is full of forces. The force of gravity, the force of momentum, the force of friction. But one thing is very simple. For every action there is an equal and opposite reaction. This is one of Issac Newtons three laws, and the reason your car slowly comes to a stop while you don't press on the gas or break. Because when no extra forces are acting, the car will become a balanced force. This means that it isn't doing anything, because the force it is putting out is equal to the force being put on it.

Try this. Put you hand on a countertop. Does it move? Probably not, right? That is because the force being put on the countertop is being equaled by other means, in this case probably supports underneath it. So the force you are putting on it is being balanced. Balanced forces.

I believe I can fly...and bounce!

Nothing like a group of Juniors and Seniors playing with a rubber bouncy ball in the hallway, right!?!? But this wasn't just bouncing a ball off a wall for the heck of it. This was seeing how high the ball would bounce from certain distances. Each group did their own thing, some had a different ball, different groups had different heights that they picked, but you had to figure out a way to see how it bounced back up. After which, we graphed our data, looking for a pattern. Our eventual goal? To predict the bounce of our ball if we dropped from the FPAC Balcony.

Procedure:
We had to repeat a process of dropping a ball and recording its initial bounce height 10 times. On ones that we were unsure of, we would redo the bounce, so that we could rerecord with a measuring stick. Using the camera, we could slow the video down on replay to a frame by frame view, so that we could see exactly how high it bounced.

After recording ten of these trials from different heights, we went to the whiteboard, where we wrote down our results for the class, as well as graphing them. We found the slope with the equation

bounces=.9(drop)+1

And then the challenge. Could we turn our data into a reasonable prediction for a 5m drop from the FPAC Balcony. Logic would say "just insert numbers into the slope equation and you will get a prediction," right? But I chose a different approach. A 5m drop is equal to 500cm. During our testing, we dropped a ball from 220cm, and got a bounce back of 144cm. We also dropped from 60cm, with a bounce of 53cm. So I took the bounce of 144cm, and multiplied it by 2, and then added the bounce of 53cm, for a total of 341cm bounce on an accumulated bounce of 500cm. Then, I noticed a pattern. The higher the drop, the farther the bounce height was from the drop height. For example, there was a difference of 76cm between the 220cm drop height and the 144cm bounce height. So I tried to estimate for that pattern and estimated around 335cm for the bounce height on a 500cm drop.

Turns out I overthought that a little. The bounce was actually 360cm, so the initial estimate would have been fine, but both of my estimates were closer than the slope formula.

Somebody check the Buggy's license. It's tumbling a lot.

Ok, so before there was technology to measure our motion for us, there was...wood, iron and...nevermind. It's a measuring stick, tape and a stopwatch. Just as good as motion detectors, right? Although, much harder to be precise. After being given our Tumble buggy, we had to find a spot to work, like out in the hall. And the lab? Measure how far the Tumble buggy could go in certain amounts of time. Easy enough, right? Once we marked out where the Cart would be started each time, we had one person in our group start the buggy, and one with the watch. But two things came up. 

1) Starting the watch and the buggy at the same time, and then stopping them at the same time and;

2) whoever is driving that Tumble Buggy CAN'T DRIVE STRAIGHT!

We started using a countdown before starting the buggy, and then had the person with the watch stop the buggy. Still not 100% accurate, but we had to try and get it as close to accurate, and consistent as we could. But the other problem made us think. With the cart turning off to the side, should we try and keep it straight? Would that interfere with the results? Was the cart turning part of the trial, and should be treated as part of the normal motions? Well, if we touched the cart during it's timed runs, it left the thought about skewing the data. Because if it slows down, or speeds up, because it got bumped by us, or something we placed, that would change the outcome. So that wouldn't work. But if we left it, would it remain consistent? Could that be considered part of the cart's motion, and therefore be left in the data as a totally valid factor? 

As it turned out, we calculated the cart distance by how far, in a straight line, it traveled. So even though it curved, we marked where it stopped, and measured straight from the start, to a spot which was in line with where it stopped. We felt that that was the most consistent way to handle the curve, without skewing the data.