Turbines - A Long WINDed Process

In my physics class, we made wind turbines to wind down the year.  Having just learned about magnetism and the basic concepts of generators and motors, the turbines were not very complicated for us to build.

Background Information:

Wind turbines are used to capture solar energy (wind) to create mechanical energy (the turning of the repellers) and then turn this mechanical energy into electrical energy. The wind turns the repellers which then becomes the input mechanical energy into a simple generator. This is done by rotating magnets that are surrounded by coils of wire. The magnets cause a change in the magnetic field as they move, as in our design we alternated the magnets between north and south poles so that the change was greater. The change in magnetic fields induces a voltage in the coils of wire which causes an electric current. This is how wind turbines generate energy that we are conveniently able to use.

Materials and Methods:

My group used the following materials:
PVC pipe
wooden rods, 2 different sizes
cardboard
wire coil
4 small magnets
two round wooden attachments, two different sizes

We used the PVC pipe as the "tower" of our turbine. Then we used two PVC attachment pieces to create a "neck" at the top of the tower which would house the basic generator we made and connect to our wind catching device. We created blades by hot glueing pieces of cardboard to three wooden rods. We then cut the tips of these rods so that they had a flat surface and we used wood glue to fasten them to a wooden connector piece, the type that is typically used for a knob of some sort. To reinforce the glue, we put a screw through the rods. Tis connector piece has a hole in its center which we widened with a drill. Through this hole we slid another, thinner, wooden rod. We put another smaller wooden connector piece on this rod as well, towards the center of the rod. This piece had four small magnets glued onto it, evenly spaced. The north side of two of the magnets was facing out, while the south side of the other two was facing out. We were sure to alternate the polarity in order to create a consistently changing magnetic field. This piece with the magnets was placed just over the wire coils so that they could affect it with their magnetic field. The wooden rod that held this piece continued through this tunnel of PVC pipe and out the other end. On each side we put a small cardboard disk with a hole drilled in it for the rod to go through so that we could keep the repellers and the magnets suspended. The wire coil was pretty thick so that we could generate voltage. Each end of the wire had to be sticking out so that we could measure the changing voltage and see if our turbine was working. We ran one end of the wire down the PVC tower and taped it to the outside of the pipe. The other end we stuck out the PVC attachments at the "neck" region of the turbine. We scraped the outside of the wire off so that voltage could be read.

Results and Discussion:

The amount of voltage induced by our turbine was effected by the thickness of the coil of wire- or how many turns it had. We wrapped ours for a long time, we did not count the turns but it is suggested that when in doubt, keep wrapping. Also the magnets had to alternate in polarity. This was a problem because the magnets wanted to keep sticking together. We had to cover them with our hands while we were glueing them onto the wooden attachment. Hot glue worked fine but I would advise keeping the magnets away from metallic items once they have been glued on- we had some problems with this and had to re-glue. Keeping our design as simple as possible worked out well for my group. The cardboard worked just dandy as a way of keeping the rod in place that attached the spinning device to the magnet. Our biggest difficulty was inserting the coil into the turbine but we were lucky to have built the tower and neck parts with easily detachable pieces. We forgot to leave both ends of the coil out so that is something to keep in mind when designing your turbine and wrapping your coil.

Here's a video of our turbine in action:

Unit 7 Summary

We began this unit learning about magnetism. The source of all magnetism is moving charges. These charges, electrons, spin in completely random directions when they are not magnetized. Domains are clusters of electrons that are all spinning in the same way. They have no net direction until they are affected by a magnetic field; when magnetized, domains align so that the magnetic field can continue to flow. In each magnetic field, there are two poles- north and south. The magnetic field always comes from the north pole to the south and goes from the south to north.

It is also important to know that the poles are like charges in that like poles repel while opposite poles attract. This is because the magnetic field lines flow towards the opposite poles and repel from the ones that are like the pole they just left.

One of the big questions we asked with this section was : why do paper clips stick to magnets?

A paperclip that is not magnetized will have domains pointing in all different directions. A magnet has a magnetic field. When the magnet is close to the paperclip, the domains of the paperclip align to match the magnetic field of the magnet. The paperclip now has a north ad south pole, just like the magnet. The north pole of the paperclip is attracted to the south pole of the magnet and thus the paperclip sticks to the magnet. Now, the paperclip can act as a magnet and other paperclips stick to it, their domains also aligning to match the magnetic field.

A fun fact about magnetic poles is that the Earth's magnetic south pole is actually at the top of the Earth, which we generally consider the geographic north pole. The Earth's magnetic north pole is on the Earth's bottom, at the southern tip.

All moving charges feel a pull from a magnetic field if they are moving perpendicular to it. The Aurora Borealis, or the Northern Lights, are actually cosmic radiation- moving charges from space that got sucked into Earth's magnetic field and spiral around the field lines and into the Earth's magnetic poles. This is why we can see them in northern parts of the world- they are following the magnetic field lines into the south pole.

Any moving charge that is moving perpendicular to a magnetic field will feel a force from it. this brings us to the "right-hand rule" that explains the relationship between current, force, and magnetic fields. 

In this picture, my pointer finger represents the direction of the current of moving charges. My middle finger represents the direction of the magnetic field and my thumb shows the perpendicular direction that the charges will be caused to move in.

Electromagnetic induction is the process of inducing voltage by changing the magnetic field in loops of wire. Voltage is induced by the motion between wire and magnetic field. The more loops of wire, the greater the voltage that is induced. This is summarized in Faraday's Law, which states that:

The induced voltage in a coil is proportional to the product of its number of loops, the cross-sectional area of each loop, and the rate at which the magnetic field changes within these loops.

There are three ways that voltage can be induced in a wire:

1) moving the loop of wire near a magnet

2) moving a magnet near the loop of wire

3) changing the current in a nearby loop

All of these methods involve changing the magnetic field in the loop of wire.

 This process is used in transformers. Transformers utilize a primary coil, which receive the input of electric current, and a secondary coil, which has an output of electric current. When electric current flows through the primary coil, it causes a change in the coil's magnetic field which spreads and induces voltage in the secondary coil. Voltage causes current, so the electric current is thus transferred between coils. The current must be ac for a transformer to work because this has a constantly changing current, so the magnetic field is constantly changing, which is the only way for the transfer of electricity to be constant. Transformers can either step voltage up or down, depending on the electric power required. The relationship between primary and secondary voltages is described in the equation:

The conservation of energy, which we learned in a pervious unit, comes into play here as well. The initial amount of energy must be equivalent to the ending amount as energy cannot be created. Power is the rate at which energy is transferred. Therefore, the power into the primary coil = the power out of the secondary coil. Electric power = voltage x current. Thus:

primary (Voltage x Current) =  secondary (Voltage x Current).

If the secondary coil has a greater voltage than the primary coil, it will have a weaker current, and vice versa.

Finally, we learned about generators and motors. They work in opposite ways, to put it simply. Generators have an input of mechanical energy, and through electromagnetic induction, have an output of electric energy. They are made of coils of wire and magnets (much like transformers). Motors take electric energy (the input) and through electromagnetic induction produce mechanical energy (the output). They are also made of coils of wire and magnets. The generator effect is: current as a result of motion. The motor effect is: motion as a result of current.

Simple Motors

This week, our class took a leap and designed our own motors. We followed a fairly simple design, which was powered by a 1.5 volt battery and a small magnet. Paper clips were attached to each end of the battery and held a coil of wire; they helped complete the circuit and connect the positive and negative ends of the battery. 

Th current flows from the battery, up one paper clip, through the wire and the motor loop and then back down the other paper clip and back to the battery. Each part of the motor functioned in a different way. The battery supplied voltage to produce a current. The coil of wire, or the motor loop as it is labeled in the diagram above, provided a pathway that allowed current to flow. The paperclips connected the wire to the batter and completed the circuit, also allowing current to flow. The magnet, placed on top of the battery, created a magnetic field that put magnetic force on the motor loop and caused it to turn.

Here is a picture of our actual motor:

We scraped one side of the wire that connected the coil to the paper clip. We did this because we needed current to flow when the loop was in one orientation and not the other. We wanted it to flow while the loop was turning in one direction without causing the loop to turn in the other direction as this would be counterproductive.

The motor turned because of the magnetic pull created by the magnet. The loop had to be vertical. This is because all the charges in the wire were moving the same way, but since the wire was coiled the current would technically be in different directions (this is important when using the right hand rule). The vertical loop felt the force of the magnet in opposite directions on the top and the bottom sides so there was a torque on both ends of the wire, causing it to rotate. If the loop was horizontal, it would not feel this force in a perpendicular way and there would be no rotation. Along the bottom of the vertical loop, the current was going to the right. (This is form the viewer's perspective in the photo above). According to the right hand rule, the magnetic field would be in the upward direction, and the force on the wire would be towards the viewer. On the top of the loop, the current would be going back the other way, the magnetic field is still in the upward direction, and the force on the wire would be in the opposite direction, away from the viewer. Since the sides of the wire are pushed in opposite directions, the wire rotates. When the wire flips and the current is still going in different directions, the magnetic field continues to act on it in this way.

Here is a picture of the hand position for the "Right Hand Rule":

My pointer finger represents the direction of the current, my middle finger represents the direction of the magnetic field, and my thumb represents the direction of the force. In order to find one of these, all you have to do is put your right hand in this position and turn it in the correct way to align with the current, force, or magnetic field given.

This motor is very small, in fact it is too small to effectively power anything. However, it can be used for educational purposes and effectively displays the basic concepts of a motor and how a simple motor is built and works. Plus it is pretty cool to watch- check out this video of ours in action!

Unit 6 Blog Reflection

This unit focused mainly on electricity and the different components that make our electrically powered appliances work.

Some important terms to know:

Current - a current allows for the movement of charges. A current flows through every part of the circuit at the same time.

Conductor - conductors allow charges to flow freely

Insulator - insulators do not allow charges to move freely

The first concept we covered was the concept of charge and polarization. Positive charges are held in protons while negative charges are held in electrons. If an object has more electrons than protons, then it is negatively charged, and vice versa. It is important to know that like charges repel each other while opposite charges attract each other. There are 3 ways to charge an object:

1) Direct Contact

2) Friction

3) Induction

Direct contact is self-explanatory in that objects transfer charges by touching each other, leaving the objects with a net positive or negative charge.

Friction occurs by rubbing objects together. Electrons are “borrowed,” they move from one object to the other.

Induction is a bit different. In induction, there is no contact between the objects. There is a neutral object and another charged object comes very close to it. The like charges are repelled and the opposite charges are attracted to the charged object. This causes the neutral object to polarize, meaning its charges separate. The opposite charges are still attracted to the charged object while the like charges are repelled and find the easiest path to the ground, fleeing the once neutral object. This object is then charged.

Lightning is believed to be a product of induction. In a storm, the clouds are heavy and rub together. The friction causes the clouds to polarize with negative charges on the bottom and positive charges on the top. The strength of these charges causes the ground to polarize as well, with positive charges on the surface (because they are opposite and attracted to the negative charges) and negative charges deep into the ground. The attraction between the opposite charges of the bottom of the cloud and the surface of the ground is strong and the charges want to equalize. When enough energy can flow through the electric field created between the cloud and the earth, the charges equalize through the air. The lightning is the result of the release of this energy. Lightning rods work by providing the easiest path to the ground for the lightning to follow. The ground is positive and the lightning rod conducts the positive charges to the highest point so that the lightning is attracted to it.

Plastic wrap sticks to bowls because of induction as well. The wrap is negatively charged by friction and when brought near the bowl, the bowl polarizes. The positive charges in the bowl move close to the negative charges of the plastic while the negative charges of the bowl move away. The distance between the opposite attractive charges is smaller than the distance between the like repellant charges. Since there is a greater distance between the repulsive charges, the force between them is less than the force between the closer attractive forced because, according to Coulomb’s law, force is inversely proportional to distance squared so the smaller the distance the stronger the force and vice versa. Thus the plastic wrap sticks to the bowl because of the strong force between the attractive charges.

There is a problem similar to this one that involves a balloon sticking to the wall. The only difference really is that the balloon is first charged by friction. This problem is a big one!

Coulomb’s Law is also very important to this section. It states that the force between any two charges is inversely proportional to the distance.

F= k q1q2 / d^2

Note: it is very important to remember to square the distance!!

Along with charges and such we learned that dryer sheets are used to reduce or prevent static cling in your laundry. They coat the clothes so that friction does not charge them when they rub together in the dryer. This was a fun fact, in my opinion.

Next we learned about electric fields, which are the area around a charge that can influence another charge. We usually talk about electric fields in relation to positive charges and how they influence them.

The equation used to find the force of an electric field is: E = F / q (force per Coulomb)

Note: q is the symbol for charge or Coulombs in equations.

Electric fields are drawn with arrows pointing in the direction of force the field will have on a positive charge. This tells us whether the charge that the electric field is centered around is negative or positive- if it is positive, the arrows will point out, if it is negative, the arrows will be pointing in towards the center. The farther out the arrows are, the weaker the force that the field has on the positive charge is. The arrows themselves display this visually as they get more widespread the further from the center they get.

When an object is on the inside of an electric field in a way that it is not affected by outside charges and it has no net force on it because it is either pulled strongly by a few close charges or less strongly by a ton of distant charges, this is called electric shielding. When you are in a car during a thunderstorm, you do not get struck by lightning because the car acts as an electric shield.

Our next big topic was voltage. Voltage, or electric potential energy difference, is the difference in potential energy between two points. It is also a measure of how much energy we can get out of one Coulomb of charge. The larger the difference in charges, the larger the difference in potential energy and, consequently, the possible change in kinetic energy is greater.

Voltage equals the potential energy difference per Coulomb of charge.

V = ∆PE / q

As for units, voltage is measured in volts (big surprise), which are equal to Joules per Coulomb (energy per charge).

Ohm’s Law described the relationship between voltage and current by putting it into an equation with resistance. Resistance slows down the current and weakens it. The stronger the resistance, the weaker the current. The stronger the voltage, the stronger the current. Therefore, voltage and current are directly proportional because voltage is the source of current, while current and resistance are inversely proportional.

Current = voltage / resistance.

I = V/ R.

Current is measured in amperes, voltage is measured in volts, and resistance is measure in ohms. This equation can be rearranged to solve for any of the variables.

To add on to resistance:

Resistance can be increased by lengthening or making thinner the filament of the bulb that the current flows through. Also, resistance increases as temperature increases. This is why you are more likely to burst a bulb right when you turn a light on because as time goes on the resistance increases and the bulb gets hotter and dimmer. A high wattage bulb, however, will have a higher voltage thus a stronger current and less resistance. It will be brighter.

To wrap up the unit we learned about circuitry. Circuits are the pathways that currents flow through. The entire current flows at once through a circuit and will always take the path of least resistance. There are two types of currents that we learned about. The first, direct current (dc), is comprised of charges flowing in one direction. DC is always used in batteries. The other type, alternating current (ac), electrons move in one direction first and then in the opposite direction. This is done by alternating the polarity of the voltage causing the current at the voltage source. AC is typically used in commercial items and household currents are ac. A diode is a tiny electronic device that acts as a one-way valve to allow electron flow in one direction only. AC changes every half cycle so the current passes through the diode half of each period. The output here is a rough dc and it is off half of the time. Capacitors are used to maintain a continuous current and smooth out the bumps.

Capacitors are made up of two plates that store charge. They transfer electrons between each other for a while, taking time to build up a charge. They the release strong currents and have to build up again. An example of this is a camera flash- you have to wait between flashes because it takes the capacitors time to reload.

The net flow of electrons is referred to as drift velocity.

Electric power is the rate at which electric energy is converted into another form. The equation for power that we already knew is:

Power = energy / time.

The new equation that we use puts power into the context of current and voltage.

Power = current x voltage.

Just as there are ac and dc currents, there are different types of circuits that can be constructed. A series circuit has every appliance attached in the same current to the voltage source. A parallel circuit, however, splits the current between each appliance.

The more appliances that are added to series circuits, the greater the resistance. The current per appliance decreases so each appliance gets weaker/dimmer. Parallel circuits work in the opposite way. Each appliance that is added brings more current to the circuit. As more appliances are added, the current increases, the resistance decreases (it is halved as more appliances are added) and the voltage stays the same. In a series, if one light bulb is removed, none of the bulbs can work because the circuit has been broken. In parallel, appliances can be removed and the rest will work fine. All homes are wired with parallel circuits.

Fuses are made to protect circuits. They connect the circuit and current flows through them- when the current gets too strong and overheats, the fuse breaks and thus breaks the circuit so no more current can flow to the appliances. The fuse is attached to the series circuit with no problem and must be attached to the series part of the parallel circuit so that it controls the current to all appliances connected.

What I found difficult about what we studied in this unit was the concept of capacitors and the energy difference part of voltage. This really tripped me up but Mr. Rue re-explained both concepts in review sessions; hearing the information a second time and in a different way helped me to process it and return to the information, understanding it better the second time.

My effort towards quizzes in this unit really paid off and I am glad that I studied for all the quizzes this unit. Next unit, I hope to keep up with my daily homework better and be more consistent and thorough with homework assignments- it is easy to get caught up in other work and to rush through or to not finish the homework. I think I contributed to class heavily, just as I have been for the rest of the year. I do, however, need to work on explaining concepts concisely and clearly.

This unit connected heavily to my daily life because I use electricity all day and I never even knew how many natural physics processes occurred (even just by turning on a light). The most relevant and interesting thing for me was how light bulbs are lit and how circuits are constructed as it clarifies for me how my everyday appliances are working and how they are powered.

(This unit we did not have time for a podcast, but next maybe time!)

Current

Current refers to the flow of electrons in a circuit. Current is caused by voltage, or potential energy difference. Current and voltage are directly related, while current and resistance are inversely related. Resistance is what slows down or weakens a current. This can all be summed up in Ohm's Law: Current = Voltage / Resistance. The greater the voltage, the stronger the current, the greater the resistance, the weaker the current.

While the video below is a bit longer than most of the resources I use, I think the speaker really explains the concept of current in relation to voltage and resistance well. He speaks slowly and does not try to cram too much information into a two minute video, like some other sources tend to do. I think this video is worth the watch and definitely a helpful source!

Voltage

Voltage is the difference in potential energy between 2 points. It is a measure of how much energy we can get out of one coulomb of charge between these points. The bigger the difference in potential energy, the bigger the voltage. It is also referred to as electrical potential energy difference. This is pretty self-explanatory. I thought this video had a brief explanation of voltage but it inserted the concept nicely in context of other physics related concepts, current and power. The video did not include, however, an important equation for voltage. Voltage is equal to the change in potential energy per Coulomb of charge which is written as V = ∆PE / q. Potential energy is measured in Joules and charge (q) is measured in Coulombs so one unit of voltage (aside from volts) is Joules per Coulomb (J/c).

Mousetrap Car

Our Mousetrap car looked like this:

Our car came in 2nd place out of all the cars in our class with a time of 3.72 seconds (this is how long it took the car to go five meters.)

Physics of a Mousetrap Car:

Newton’s First Law- an object in motion tends to stay in motion and an object at rest will stay at rest unless acted upon by an outside force

Newton’s Second Law – a=f/m

The greater the force and the less the mass of the car, the greater the acceleration it will have; this is according to Newton’s 2^nd law because acceleration is directly proportional to force and inversely proportional to mass. We took this into account when constructing our car. Although we did not do much to increase the force, mainly relying on the force generated by the mousetrap being triggered, we considered the mass in every aspect of building our car. We tried to use all lightweight materials. We hollowed out Bic pens because they are very light plastic, we used CD’s because they are thin and lightweight, and we did not add anything to the base and used only the mass of the mousetrap itself because this was as light as we could possibly build the base.

Newton’s Third Law – every action has an equal and opposite reaction. When the wheels of the car (formed by CD’s in this case) push the ground backwards, the ground pushes the wheels forward so the car moves.

The two types of friction present are static and kinetic. The problems we encountered with friction occurred when we put balloons on all four of the wheels. This slowed the car down a lot and made it very hard for the car to move because there was too much friction with the ground. We used friction to our advantage by putting balloons around the back wheels to stabilize the CD’s so that they do not slide around on the ground. This allows us to have a better force to propel the car coming form the back rather than the front, which would be less effective.

We based our design off another homemade design we found on the Internet. This design used four wheels which we thought made sense as the car would be stable and not wobbly as we suspected it would be with less wheels. We had two axles with two wheels on each axle. Our wheels were CD’s. As I said before, we figured that lightweight materials would be best so CD’s made sense to us to use. Also they were larger than a different kind of wheel, such as a bottle cap, would have been. The larger something is in diameter, the further its edges are from the center or axis of rotation. This means the object will have a greater tangential velocity and thus cover more distance in the same amount of time. Our CD’s definitely had a greater tangential velocity than most of the other cars’ wheels, as they were much smaller. I think this added greatly to our car’s speed.

Rotational inertia is an object’s resistance to spin. The more rotational inertia an object has, the harder it is for the object to spin. We wanted to decrease the rotational inertia of our car’s wheels and axles as much as we could. We put balloons around the edge of the back two wheels so they would have better traction but we did not put them around the front wheels because we found that this added to the rotational inertia of the CD’s and prevented the car from making any measurable progress. The rotational velocity of both the front and back sets of wheels was made to be the same by using identical axles and wheels. We wanted the wheels to move together as we would be able to better predict results.

Conservation of energy is the principal that the change in potential energy is equal to the change in kinetic energy as an object goes from being at rest to being in movement. The maximum amount of kinetic energy that our car could possibly have would be the amount of potential energy it had when it was at rest. Potential energy is equal to mass x gravity x height. In order to have potential energy, the object must have some height to it. Also, the maximum amount of potential energy that our car would have would be when it was at rest. Right before we triggered the mousetrap would be a great moment to determine the potential energy from. As the car launches into movement after being triggered, the potential energy decreases and the kinetic energy increases. Energy is the car’s ability to do work so as the kinetic energy of the car increased, the work hat the car was doing increased as well (∆KE = work). Work is equal to force x distance, so the car was exerting more force and going a further distance with the increase of the work it was doing. Following this logic, it would be best to have a car with a lot of potential energy to start off so that it will have more kinetic energy, do more work, and go further.

The lever arm on our car was the mousetrap itself. The metal part that physically snaps was what rotated on our car. Instead of using the torque from this lever arm to lead the car the entire race, as many of our peers did, we used the lever arm to spin the axle at its moment of triggering. To do so we attached a string to the lever arm which was wound around the back axle. The axle spun as the string unraveled and set the wheels into motion. The lever arm was our main pulling force even though it only acted for a short amount of time. Power is work over time. The power output of our car was not very much as it did not go very fast. This may have been due to the fact that our lever arm did not continue to pull the car throughout the entirety of its run. However, it did set the car into motion and thus initiated any power generated.

To calculate the exact amount of work that the spring did on the car, we would need to know the distance it took to stop the spring. We would also need to know the exact force it exerted. Since we do not know the distance, we cannot calculate the work the spring did or if it even did any work. To calculate the amount of potential energy stored in the spring, we would need to know the height and to find this we would need to find a solid starting point for measuring this distance. If we do not know the potential energy, we cannot calculate the kinetic energy easily because ∆KE = ∆PE. Also ∆KE = work, so without knowing the work or the potential energy of the spring, it would be difficult to find the kinetic energy.

Reflection:

Our final design only differed slightly from our original design. We replaced the soda caps with zip ties because the caps were not the right shape and did not fit the axle or properly keep the axle from moving. Their original purpose was to stabilize the axles so that the CD’s would move in one line. We put zip ties on because they stayed in place so that the axles did not move too much (they were on the inside of the eye hooks that attached the axles to the mousetrap so that the axle could not move much horizontally as the zip ties would catch at the eye hooks). Also, zip ties were small enough that they did not hit the mousetrap base as they rotated with the axle, which was a problem we encountered with the soda caps. I would not recommend using soda caps for this purpose as they were difficult to work with.

The major problem with our car was that it was unreliable and did not follow a straight path. The sources of this problem were the wheels as they were only slightly off center and turned a bit to the side. To solve this, we tried to create tape barriers to correct the curving of the CD’s. This did not work very well but it got the job done. I would have liked to reconstruct the way the CD’s were attached to the axles however this problem did not arise until the final day of the project and time was of the essence.

If I were to do this project again, I would like to try a design similar to that of most of my peers. Most of the other groups created a lever arm that rotated as the car covered distance and gradually unraveled the string to make the axle spin. I am not sure how much faster this would make our car but I think if it was well built it would be a great design. However, I liked my group’s design a lot as it was unique and worked very well in theory. The main things I would change are that I would make the base longer so that the CD wheels had no possibility of touching. This was a slight problem for us that we adjusted by placing the CD’s at different intervals along the axles but it did cause a slight road bump. I would also find a more reliable way to attach the CD’s to the Bic pen axles. We used masking tape wound thickly around the pens to make a thick thing that the CD could fit snugly around as it would rotate with the axles. The tape bunched and snagged when we tried to put the CD on it. I would like to find a way to perfect this and make it more practical and easier to make.

Here are some videos of my group's mousetrap car in action!