Mouse Trap Car: Day1

Today was our first day of construction on the mousetrap car! Natalia and I started by attempting to remove the wheels from the toy car that we bought, thinking that the wheels would provide and realistic aspect to the car (and also add some speed!) With high hopes we began to take apart the car, hoping to easily take the wheels off, but that is the opposite of what happened. We used a screwdriver, our bare hands, a drill, and even a hammer, but it was very hard (almost impossible!) to separate the wheels from the car, and once we finally did get them separated, we discovered that their was no axel connecting the wheels, and instead some screws! That was upsetting, but we decided to come up with a new plan. Using a wooden stick that we bought at Lowes, we decided to make our own axel for the car my using a drill to drill holes in the wheels, providing a hole to put the stick through. This ultimately will connect our mousetrap car. Although we did not get much done because of the unplanned for difficulties, we are one step closer to creating our mousetrap car!

Mouse Trap Car: Supplies

The Mousetrap car project was an unexpected challenge! Both my partner and myself have never made, let alone heard of a mousetrap car, but with some helpful videos on YouTube such as this one.I was able to understand that a mousetrap car is actually built using a mousetrap as the “engine”. In the video the creation of a mousetrap car is shown successfully. By taking some of the videos information and also using our physics knowledge, we will be able to create a mousetrap car in order to win this race we must create a practical but fast car.  Here is a list of supplies needed for the winning car…

1.   .Eye hooks (used to connect the car and wheels by drilling small holes into the mousetrap car)

2.    A mousetrap!

3.   Wheels (we decided to use wheels from a toy truck bought at the dollar store, because the wheels would act as more realistic wheels than wheels we made ourselves)

4.    A thin wooden stick to increase the lever arm of the mousetrap to give a greater force to propel the contraption

5.    Zip ties to act as an adhesive for the mousetrap’s wheels

6.    Fishing line

The car that we bought to disassemble and use the wheels for our own car!

Once we have all of these items, we will be ready to begin assembling the car, and eventually win the race!

Physics Reflection 1/30/12

This section we began by learning Circular Motion, which is comprised of tangential and rotational speed.

Tangential speed- a linear speed of something moving in a circular path

Rotational Speed- Number of Rotations on the axis of revolutions per unit of time.

With this, I learned that tangential speed is directly proportional to rotational speed. Knowing this basic information, as a class we moved on to learning about the axis of rotation.  In this section we learned that the farther from, the axis of rotation you are, the faster you, must move to keep up with the rotations. A great example of this is when you roll a tapered cup across a table, the path of the cup will curve because the wider end will roll faster in order to have the same revolutions per minute as the smaller end, meaning that it will cover more distance in the same time, so its tangential speed is greater!  I then learned about rotational inertia and why a wooden ball will go down a ramp faster than a hoop. The reason is that in a wooden ball, its center of mass is at the center of the ball, thus giving it a very small rotational inertia, and a large rotational velocity meaning that the wooden ball will be, much easier to begin rotating than the hoop. After learning about that, we moved on to center of mass, gravity, and torque! During this time I learned that you stretch your arms out while walking on a balance beam, because it increases the rotational inertia and gives a wider range of where your center of mass is. It also balances your torque by giving yourself a lever arm!

Torque=lever arm x force

Counterclockwise torque=clockwise torque

Now, on to Center of Gravity!

Center of Gravity- where gravity causes the force (torques are equal)

IU learned here that when you have a lower center of gravity you are more stable because your feet act as the axis of rotation.

Centrifugal Force- a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving

What I found difficult:

This section, we worked with many different concepts, but the area that I thought was especially hard to understand was Centrifugal motion and Centripetal force. When we first learned about the two it was hard to differentiate the two, and I was confused about what exactly Centripetal force is. I now know that centrifugal force is an outside force, and is really the absence of a force instead of an actual force, and centripetal force is the force pulling something towards the middle. I learned this in the washer and dryer problem. The reason that clothes become dry in a washing machine is because when the water and clothes are in the machine they both have the same tangential velocity. The water is able to go through the holes on the sides of the washing machine and as a result of inertia the water will continue to move in a straight line through the holes. Friction will then act on the clothes as a centripetal force and push the clothes inward, drying the clothes! It was hard to grasp the concept of the two forces, but I was able to through practicing many problems and reading the information in my textbook

Connections to the real world:

I really connected my street smarts with physics when we learned about how tangential and rotational velocity affect the train tracks, which was able for me to connect to very easily. I learned why train wheels are built. The reason is, that when a train travels down a track it stays on the track because the wheels correct themselves due to the taper in the wheel because the larger end is on the inside of the tracks and must move tangential faster than the outside to keep up with the rotational speed, and in doing so makes tiny corrections within the tracks to keep the train stable. 

I also learned in centrifugal force about the movement people make in cars, which is very relatable to me! I learned that the centrifugal force does not push you against the car, but the reason that you hit the side of the car is because no force is acting upon you. When the car is turning you continue in a straight path as a result of inertia. The car door then hits you and forces you towards the center of the circle the car were making. Now I know what happens when cars move!

Problem Solving Skills:

This section was not so much of a problem, solving section, as it was a critical thinking section. Centrifugal force and center of gravity required you to think about the world around you, with out as much math as critical thinking. Thus section was very advantageous to me though because I feel as though I know much more about daily life instances like why gymnasts are often shorter, which is because their center of gravity is lower, making their center of mass wider than that of a tall person. I also found the centripetal force useful to know. Next time I am, riding in a car and we round a turn I will know that the car is actually hitting me in order to push me towards the center of the circle the car is trying to make! I have realized over thus past semester in physics that science is all around us!

MASS OF A METERSTICK LAB

Meter stick Lab

Objective: To Find the Mass of a meterstick using only a 100 gram weight

Step 1

1.     Torque= lever arm times force, so in order to find the mass of the meterstick, you must first know the torque, by balancing the stick, so that the stick reads 50 cm.

2.     Once you know the center of mass (middle of stick) you can use the 100 g weight for trial and error by setting the weight on the very edge of the stick

3.     Once you find where the torques are equal when involving the 100 gram weight, you will be given the lever arms of both sides. The first lever arm will be that from the point where the table balances to the weight, while the other lever arm will be from the point of balance to the center of mass. (50 cm)

4.     Knowing the lever arms, and the force for one side, I can go back and create an equation to figure out the force of the other side. Lets say…

The lever arm of side a times the force of side a set equal to the lever arm of side b times x (the force)

5.     Once you know the torque of both sides, you can find the mass by adding the torques together and then multiplying them both by the force of gravity (9.8N)

Step 2

Torque- lever arm x force

1.     First I weight the side with the 100g weight, and measure the lever arm (the point from where the weight is to where the torques are balanced)

·            Lever arm= 30cmx100g (force)= 3000

2.     Side without weight

·            Lever arm- 20cm (from where the torques are balanced to the center of mass of the meterstick is)

·            Then, I can use the equation 20x=30x1000 (setting the torques equal)

This equals=1500k=force of side with the weight= 1500kg

then to find the mass of gravity, I used 9.8N

(9.8)x.100kgx29.4=.150(9.8)x20

using the equation w=mg, I found that .98=m for the side not containing the weight

·            Then to find the mass for the side without the weight, I also used the equation w=mg

So, 1.47kg=m

Adding the masses together I found that the entire mass of the meterstick is 2.45kg, this is after establishing that I needed to incorporate the force of gravity, and that I used the wrong decimal during my first attempts

I found that the method that I showed above worked, because I used the torques, which I set equal to find the weight of the entire stick using w=mg, eventually giving me the mass of the meterstick. Earlier this week in class, we learned that just because torques are equal, it does not mean that the weights or masses are equal. Torques only take into factor the lever arm and force, in this lab I had to learn how to apply torque to find the mass of an object. The reason that the meterstick balanced when the 100g weight was applied was because although the center of mass of the meter stick is at the 50cm mark, when the force was applied, the lever arm decreased because torque=lever arm xforce, and the two are indirectly proportional.  On the other side without the weight, their was not a lot of force meaning that the lever arm increased, thus equaling out overall in the torque.

PREZI FOR SECTION 4!

here's the link!

http://prezi.com/tlhscovsolwc/physics-unit-4-reflection/

Link To Prezi!

Here is the link to my prezi. Enjoy!
Deane

http://prezi.com/yrn0sewojspk/copy-of-physics-unit-3-reflection/

Physics Reflection For Section 2

             What I learned…
               This chapter, I learned more than I thought was possible! From parabolas to acceleration, I feel that as a class we are getting more in depth with physics. Starting with Newton’s second law, i felt things were getting more complicated, but more interesting. I learned that acceleration is equal to the net force over the mass, and also that acceleration in equation equals gravity! (a=g). I also learned how to find the distance of something falling (d=1/2gt²) and its velocity (v=gt). After this, we look a bid leap and starting to learn about how things fall. I learned how to calculate an object velocity and distance in the air at any given moment. I also learned that in freefall, objects acceleration is always 10m/s², and that all objects fall at the same rate during freefall because there is no air resistance. Things got a little more complicated when we put air resistance into the mix, but it soon got easier. Air resistance relies on the surface area of an object (among other things), so if it has a larger surface area, then the terminal velocity (the speed it reaches so that its at equilibrium meaning the net force is the same as the air resistance) is greater. While learning about parabolas I found out that horizontal force is always constant while vertical force changing and increases.

                     What I found difficult....
              With so many new concepts this section, I felt like I was struggling a little at the beginning with parabolas and vertical motion, along with knowing how to calculate an objects height off the ground at any second while its in the air. I also struggled with learning how to calculate an objects velocity without air resistance. Learning everything about air resistance after learning about free fall was hard. One concept was so easy, while air resistance was more challenging to grasp.
            

           Problem solving skills....
               I feel that my problem solving skills have greatly improved this section. I am now able to calculate an objects height in air or how long it will take a box to drop to the ground out of a plane. I find it easier to determine which formulas to use for each problem and I am learning how to actually answer the question I am asked. While we added ne equations such as a=Fnet/m and Fnet=Fweight- Fair, I am now used to plugging them in to find the answer to questions I am asked. Every section I feel as if my problem solving skills improve more and more!

              Connections to Physics in the everyday world!
                    This entire section, everything we have learned has been relevant to the outside world. Many of our labs, such as calculating the height of Anderson demonstrated the use of physics in the real world. Like I said in the questions above, I am learning how to relate everything in the world to Physics, and I am finding that physics has to do with almost everything! Finding out how high an object will go in the air if I throw it in the air at 40 m/s is now a much simpler task than before I took your class. Even now, looking back to the test we took on the first day to assess our skills, I already feel much more confidant that I could answer those questions much more sufficiently. Most of the examples we used for net force and air resistance had to do with parachutes, skydivers, and cats anyways! Our world revolves around physics.