Top Ten Ways of Living in a Dorm

Top Ten Ways of Living in a Dorm

1) Levering your door so you can level the amount of dust in your room.

If you want to open your room so you can bring the vacuum inside, you need to prop open the door. To do that you need to create a torque -- the force that causes rotation. To prevent the door from closing again, you will need to create a large lever arm by putting the door stopper at the end of the door (closer to the handle) so it will be farther from the axis of rotation. *A lever arm is the perpendicular distance from the axis of rotation to where the force is applied* A large lever arm will prevent you from needing a large force [torque = (force)(lever arm)] such as needing to put an object in front of the door to keep it open. Now you can easily vacuum your room!

2) Friction! You've done it again!

When you want to roll a bouncy ball to your friend down the hall, it doesn't always make it to their room. This is because Newton's 1st Law states, "things in motion will stay in motion and things at rest will stay at rest unless acted upon by an outside force," and when friction (the outside force) acts on the ball it won't make it all the way to your friend's room. The ball would make it all the way to your friend's room if the ground was frictionless. 

3) Bad water pressure.. 

Newton's 2nd Law states a = f/m. If the shower head isn't pushing out the water with a large amount of force then the water won't have a large acceleration, because acceleration is directly proportional to force. To have better water pressure the water needs more acceleration when coming out of the water head, thus the water head needs to push the water out with a larger force. 

Good shower heads use Newton's 2nd Law to their advantage.. 

4) Prom struggles. 

The dorm is on a parallel circuit, so each room is individually sourced. When a device is added to the circuit the current goes up and the resistance goes down. So.. when a bunch of devices are added to the circuit the current gets really high and breaks the fuse. 

A fuse stops the current flow when it (the fuse) gets to be a certain degree of heat. When the current gets too high the fuse will burn breaking the fuse, so that the wires don't cause a fire. A fuse is only added to a parallel circuit or a series/parallel combined circuit. The fuse will break if too much current is drawn from the wall, and this will cut the current to all devices to prevent fires, because too much current causes heat which is dangerous. 

5) When after study hall you have way too much energy and start to spin around and around, but you can't quite seem to spin fast enough to satisfy yourself. How would you make yourself spin faster?

Angular momentum = (rotational inertia)(rotational velocity) so when you want a large rotational velocity you need a small rotational inertia. To get a smaller rotational inertia than you already have, you can bring your arms in closer to your body because that puts your mass closer to your axis of rotation, which decreases your rotational inertia and increases your rotational velocity, which will make you spin faster. 

Conservation of angular momentum says that angular momentum before = angular momentum after,

because angular momentum is always conserved. 

(rotational inertia)(rotational velocity) = (rotational inertia)(rotational velocity)

so...

(ROTATIONAL INERTIA)(rotational velocity) = (rotational inertia)(ROTATIONAL VELOCITY)

6) When you and your friends are goofing around in the hallway, you jump on your best friend's back. You aren't sturdy on her back and fall off. Why is that?

All objects have an average position of all their mass -- center of mass. When the center of mass goes past the base of support, the object will fall over. When you're on your friend's back, if you aren't over her base of support, then you will create a torque and will fall over. A way your friend could keep you on her back would be for her to bend her legs, because that will lower her center of gravity. When you have a higher center of gravity, you are more likely to create a torque and will fall over easier. When you're on her back, the best thing for her to do is to make herself low to the ground and wide, because that will widen her base of support and make her less likely to fall over.

7) When you take your clothes out of the washer and wonder why they're still soaking wet. 

Centripetal force is the force that makes a body follow a curved path. In a washing machine the clothes have a centripetal force and the water has a tangential velocity. Within the washer are little holes on the inside that allows water to come out when the clothes are done being washed. The water is able to come through the holes, because it continues to move in a straight line with a tangential velocity (no centripetal force). If there were no holes the water would have a centripetal force and would stay inside the washer. When you take your clothes out of the washer right after the washing cycle has finished, all of the water has not come out of the holes yet, so they're still going to be soaking wet. 

8) When you're moving out for the summer, you're trying to push a box packed full with stuff, but it won't move. 

Equilibrium is reached when an object is either at rest or moving with constant velocity. If you're pushing the box with 150N, but there is 150N of friction between the ground and the box, the box isn't going to move because 150N - 150N = 0N and equilibrium is reached at 0N. To move the box you will need your friend's help so there will be a larger force on the box than the force of friction. Even if your friend only adds 1N of force, that is still 151N vs. 150N, so the box will now move. 

9) You have a lot of homework to do so you go to the dining hall, make a sandwich, and bring it back to your room to finish studying. You now have a delicious peanut butter and jelly sandwich sitting on your desk. What forces are acting on the sandwich? (ignore plate in picture)

According to Newton's 3rd Law, "every action has an equal and opposite reaction."

1) Sandwich pulls earth up <--> earth pulls sandwich down

2) Table pushes sandwich up <--> sandwich pushes table down

10) Your hall is throwing a surprise birthday party. Your job is to blow up all the balloons, but someone runs up to you, takes a ballon, rubs it on your hair, and sticks it to the wall. How did that happen?

The balloon sticks to the wall by induction. When the ballon is rubbed on your hair it steals electrons from your hair, making your hair positive and the balloon negative. The negative charge of the ballon is attracted to the positive charge of the wall, and the other side of the wall (the negative charge of the wall) is repelled from the negative charge of the balloon. This makes the wall polarized and Coulomb's Law says F = kq^1q^2/d^2 so since the opposite charges are closer in distance than the like/repulsive charges, their force is stronger than the like/repulsive charges. Thus the balloon sticks to the wall. 

Wind Turbine

Building a Wind Turbine

Materials I used to build my wind turbine:
1) cardboard - the base and the generator box
2) copper wire - to allow current to flow
3) hot glue - glue boxes together
4) a metal rod - the axle that allows the magnets to spin as the wings spin
5) 8 small magnets - creates a magnetic field

Electromagnetic induction is when a coil of wire is brought close to a magnet, inducing a voltage, and then causing a current.

Newton's 1st Law: An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an outside force.
--> The wings stay at rest until the fan made them spin.

Newton's 2nd Law: a = f/m
--> the more force (wind) the fan applied, the faster the wings spun, and the more mass the wings had the slower they went.

Newton's 3rd Law: Every action has an equal and opposite reaction.
--> Wind pushed wings -- wings pushed wind

When the wind blows the wings it creates a torque, causing the wings to spin and thus causing the magnets to spin.

Motors convert mechanical energy into electrical energy, so when the wings spin energy is created from electromagnetic induction.

This is our model. We used a tall cardboard box as the base, so the wings could spin easily without hitting the ground.

The smaller box on top of the base is our generator. Copper wire is coiled around the box on both sides. We had to be careful to wrap both coils in the same direction, so both currents would be going in the same direction.

We stuck a metal rod through the generator box for two purposes...

1) To allow the magnets something to stick on to. 

2) To attach the wings on the ends, so when they spun the magnets would also spin thus inducing a voltage.

Inside the box are 8 small magnet - 4 on each side of the rod. Electrical tape is wrapped around them to make them stay close to each other. We want to have the same poles facing each other, so that the same poles are facing outward to create a magnetic field.

*If both north and south are facing outward, then there are two poles creating a magnetic field, which would mess up the electromagnetic induction process.

Same poles repel each other, so there is a strong repulsion when same poles are facing each other; thus we wrapped the magnets in electrical tape so it would be harder for them to get away from each other. This way the magnets can spin freely - without someone holding them together - when the axle spins as a result of the wings spinning.



The fan spins the blades, which spins the magnets in result and this changes the magnetic field of the wire. This changing of b induces a voltage and causes a current to flow resulting in a generation of electricity.

We generated .008V and .008A but we were not able to light the lightbulb, because we didn't generate enough voltage.

Factors that affect the amount of voltage induced:
1) Having both coils of copper wire wrapped in the same direction, so the current flows in the same direction in both coils.
2) Having the same poles facing outward, so they'll create a magnetic field.

One issue we ran into was friction. When our magnets spun, as a result of the wings spinning, they would rub up against the walls of the box, thus slowing down the speed of the wings.

If I were to do this project again I would make a bigger generator box, because when we needed to rearrange the magnets - when we learned that same poles need to be facing outwards - it was difficult to move them with the box being so small. I also recommend coiling the wire around your generator box as you're uncoiling it from it's original roll, because the wire gets easily tangled.

Unit 6 Summary

Magnetism 

Source of all magnetism = moving charges 

domain - a cluster of electrons all spinning in the same direction 

*Not magnetized if the domains aren't all facing the same direction.

Charges moving in a wire (AC current)

 Magnetic field lines go towards north, around the magnet and back towards south

Field lines going in the same direction will attract the magnets together.

Field lines going in opposite directions will repulse the magnets from each other.

Why does a paper clip stick to a magnet?

A domain is a cluster of electrons that are spinning in the same direction. The domains in a paper clip are randomly aligned. The magnet has a magnetic field, and when the magnet is close to the paper clip the domains of the paper clip align to match the magnetic field lines of the magnet. The paper clip now has a north and a south pole, and since opposite poles attract the north pole of the paper clip is attracted to the south pole of the magnet, and thus the paper clip sticks to the magnet. 

compass - a magnet that is free to move and respond to a magnetic field. 

*A compass' needle only moves when it encounters a different magnetic field, and it will align with that magnetic field.

Magnetic fields can exert forces on other things (usually magnets) with magnetic fields. 

*symbol for magnetic field = b

Motors 

A motor relies on current bearing wires and magnets. 

How a motor works = a current carrying wire feels a force in a magnetic field and causes a torque 

All moving charges feel a force in a magnetic field if their velocity is moving perpendicular to the magnetic field. If it's moving parallel it won't feel a force, which is how things enter our atmosphere. 

*This is why the equator is generally shielded from cosmic rays entering, and the northern countries aren't. 

Current is moving perpendicular to the magnetic field (the charges have a force from the magnetic's magnetic field).

Electromagnetic Induction

Electromagnets have a current carrying wire that has a magnetic field. The domains of an unmagnetized object can align with that field and then have a magnetic field of its own. 

Electromagnetic induction - when you bring a coil of wire near a magnet, the magnetic field of the coil will change. The induces a voltage (from electromagnetic difference) and that causes a current. 

*Used in traffic lights, airport metal detectors, credit card machines, generators, transformers, etc.

*The # of loops is directly proportional to the amount to current (2 loops = 2x current). The greater the number of loops, the greater the induced voltage. 

Voltage is caused, or induced, by the relative motion between a wire and a magnetic field. The magnetic field of a magnet moves near a stationary conductor or vise versa - the conductor moves near a stationary magnetic field. 

1) move the loop near a magnet

2) move the magnet near a loop

3) change the current in a nearby loop 

The amount of current produced by electromagnetic induction depends not only on the induced voltage, but also on the resistance of the coil and the circuit to which it's connected. 

Faraday's Law: The induced voltage in a coil is proportional to the product of its number of loops and the rate of which the magnetic field changes within the loops. 

How do credit card machines work? 

Credit card machines work by electromagnetic induction, which is when you bring a coil of wire near a magnet, the magnetic field of the coil will change. The induces a voltage (from electromagnetic difference) and that causes a current. In the machine are several loops of wire, and when the series of magnets passes through the coil a voltage is induced, which causes a current. This current acts as a signal to approve/decline the card. 

Transformers

Transformers use electromagnetic induction to either step-up or step-down the voltage. 

The primary (1) is connected to a power source.

*more loops = more V induced

*more length = more resistance

As the I changes direction the magnetic field in the primary constantly changes direction as well, and that changing b of the primary induces a voltage in the secondary and will cause a current in the secondary. 

You can't use DC current in a transformer and have to use AC current, because you need a constantly changing magnetic field, to induce the voltage thus to cause a current, so you need an alternating current. 

Generators

Generators rely on turning objects. 

1) magnets

2) coils of wire

When one end of magnet is repeatedly plunged into and back out of a coil of wire, the direction of the induced voltage alternates (AC current).

Both motors and generators use coils of wire and magnets to transform energy from one form to another, but their techniques are different. 

A motor transforms electrical energy into mechanical energy. It uses a current carrying wire that feels a force in a magnetic field and that force causes a torque.

A generator transforms mechanical energy into electrical energy. It relies on electromagnetic induction: a spinning wire over a magnet or vice versa. This creates a charge in magnetic field, induces a voltage and then causes a current. 

Self Built Motor

*A motor has current bearing wires and magnets.

*A current carrying wires feel a force in a magnetic field and that force causes a torque; that's how a motor works.

I built this contraption to allow the wire to spin freely on its own. Each part of the device serves an important purpose.

Battery - supplies voltage that supplies current

Magnet - supplies magnetic field that makes charges move

Paper clip - allows rotation of the wire while also conducting current. 

Motor loop (wire) - spins as a result of the flowing current

*I scrapped the paper clip (at the point where the wire sits on the paper clip loop *at the same point on each side*) to allow the current to flow through the wire, because otherwise the coating on the wire would get in the way. If you don't scrap the wire in the same place and on the same side on each end of the wire, the wire won't make a complete circle when spinning.

The wire spins because of moving charges. The magnetic field is going up towards the wire, the current is flowing across the wire, and thus the force is going to the side of the wire. That felt force creates a torque, so the loop spins.  

All moving charges feel a force in a magnetic field if they are moving perpendicular to the magnetic field.

*This is why the equator is generally shielded from cosmic rays entering, and the northern countries aren't. 

This motor could be used as a cake mixer. You could attach whisks to the motor loop, and then when you turn on the current, the wires will spin thus creating a cake mixer with the whisks spinning. 

Unit 5 Summary

Charges 

A charge is an unbalanced number of protons and electrons. If there is more positively charged particles than negatively charged particles or more negatively charged particles than positively charged particles, then the charge is unbalanced; it is either more negatively or positively charged. 

There are two types of charges: contact and friction.

Induction is a way to charge something without touching it.

Electricity is energy being carried by charges.

Why does your hair stand on end when you take a winter cap off?

The cap steals e- from your hair though friction, making your hair become (+) and the hat (-).

Like charged repel each other, so the hair strands repel each other and stick up. 

Why do clothes stick together in the drier?

Positive and negative charges are present when there is friction. When there aren't drier sheets in the drier with the clothes, the clothes will stick to each other because they are transferring electrons to each other. BUT when there are drier sheets, the clothes don't stick to each other, because the drier sheets steal e- from the clothes, making the sheets (-) and the clothes (+). Then the clothes are all positively charged, and like charges repel each other so the clothes don't stick to each other. 

How does lightning work?

Clouds rub up against each other and become (-) though friction. This induces a (+) charge on the ground structures. The opposite charges will creep towards each other through the air, and if the path is completed energy will rush from the ground to the sky, and release light, heat, and sound in the form of lightning and thunder. 

How do lightning rods protect structures?

Lighting rods are pointy and charges like to build up on pointy things. If the lighting strikes the rod it will channel the lighting around the house and directly to the ground. Since the charges are on the rod, the lightning will be more likely to hit the rod than the house and the house will be safe.

Polarization 

An object is polar if the charges are separated (as in the ceramic bowl and balloon problems below)

A conductor lets charges move through the object. 

An insulator stops charges from moving.

Why does plastic wrap stick to ceramic bowls?

As the plastic wrap is unrolled, it becomes charged through friction. When it comes over the bowl, the (+) charges in the bowl go toward the (-) plastic wrap because opposite charges are attracted to each other. The (-) charges in the bowl are repelled by the plastic wrap because they're like charges, so they move away from the wrap. 

Coulomb's Law says F = kq1q2/d^2 

and since the opposite attractive forces are closer in distance, the force between them is stronger than the repulsive forces, and thus the wrap sticks to the bowl. The bowl becomes polarized. 

Why does a balloon stick to the wall after bring rubbed on your hair?

The balloon is charged through friction and become (-) when rubbed on your hair. When the ballon is brought close to the wall, the (+) charges in the wall are attracted to the (-) charges in the ballon, and then (-) charges in the wall repel from the like charges in the balloon, so the wall becomes polarized. 

Coulomb's Law says F = kq1q2/d^2
and since the opposite attractive forces are closer in distance, the force between them is stronger than the repulsive forces, and thus the balloon sticks to the wall. The wall becomes polarized.

Electric Fields 

An electric field is the area around a charge that can influence another charge. 

 The arrows show which way a positive charge will be pulled. In this case, the charge is going away from the other charge because they are like charges.

The arrows show which way a positive charge will be pulled. In this case, the charge is going towards the other charge because they are opposite charges.

The closer the lines are together, the stronger the electric field. Because of Coulomb's Law...

F = kq1q2/d^2

d = F        

D = f

How does electric shielding work?

If you are inside a metal container, the charges will distribute evenly around that container. No matter where you are inside of the container you will feel no force from the electric field, because even if you're closer to a couple of the charges you are still further away from enough of them that you will feel no net force, thus your charges, electrons, and protons will all stay where they need to be. 

Why are electronics placed in metal boxes?

Metal acts as an electric shield, so the electric field inside the metal zero (neutral), so the charges in the box won't be pushed/pulled by outside charges. The charges distribute evenly within the box as the are constantly moving. All the charges in the box will have equal and opposite forces in all directions. Because of the electric shielding, the sensitive electronic equipment inside of the metal that relies on the movement of charges, since it's running on electricity, is not going to feel a force inside that metal box. If the electronic equipment wasn't inside the metal box, it would feel a net force and then the device wouldn't work anymore, because it would be forced out of position and the charges wouldn't be where they needed to be.

Why can't your flash work continuously?

Capacitors are how flash works. Two oppositely charged plates that aren't connected continually add charges to each side and increase the electric field and energy between them. When the plates are connected briefly, the energy rushes from one plate to the next, and the energy is released as light thus the flash (cameras). It takes time to build up the charge on the plates and enough stored energy in the field, so flashes can't be used continuously. 

Electric Potential 

Electric potential energy is the energy the particle posses by virtue of its location. The stored energy in electric fields.

Electric potential is the electric potential energy per unit charge --> electric potential = PE/q

*measured in volts (V)

*electric potential does not equal electric potential energy 

volt = joule/coulomb

Current is energy being carried by charges (energy flow) 

*measured in amps (A)

*current = I

*more current = more/faster movement 

Voltage is the difference in electric potential which causes current. 

*Current and voltage are proportionate.
V increases = I increases
V decreases  = I decreases

How to increase the resistance of an electric wire.

How to decrease the resistance of an electric wire.






According to Coulomb's Law, distance and force are inversely proportionate.
If the distance is doubled, the force is 1/4.
If the distance is halved, the force is 4x.
*Remember that we never manipulate the force, only the distance.

*If you double both charges in Coulomb's Law, the force will remain the same.

How can something have a higher voltage, but not be as dangerous as something with a lower voltage?

 A high voltage, but a low energy.
--> safer

A low voltage, but high energy.
--> more dangerous

Circuits 

Power = brightness measured in watts

P = IV

AC current = back and forth movement; electrons constantly dancing (plugs)

DC current = one direction moment (batteries)  

Series Circuit
--> increase in resistance
--> decrease in current

*Will draw out less current than a parallel circuit would, because 

Parallel Circuit 

--> decrease in resistance
--> increase in current


*Will draw out more current than a series circuit would, because 












Why don't birds get harmed when they stand on a wire, but would get harmed if one ran into both power line wires with it's wings?
If a bird is sitting on a wire (just one) then there isn't a complete circuit. If the bird touches both wires with it's wings then there is a complete circuit. In a complete circuit, there is a difference in electric potential and that difference causes current to flow through the bird. If there isn't a complete circuit, there won't be a difference in electric potential, so the current won't flow through the bird and it will be safe.

Why does connecting a dead battery with jumper cables to a working battery with the car running make the battery work?
When the two batteries are connected, it creates a complete circuit so the energy can be transferred from the working battery to the dead battery. This will create a difference in electric potential and will cause current to flow (even though they always have the same amount of current) so the dead battery will then work.

Why are electric wires so thick?
Being thick is a way to decrease resistance. Since resistance and current are inversely proportionate due to I = V/R when resistance decreases, current increases.  So if the wire is thick the resistance will decrease, increasing the current. If the device was a lightbulb, it would shine brighter because the current had increased.

Why is it dangerous to plug American appliances into European circuits?
American appliances are used to less voltage, and they also have a lower resistance which increases current. So when the American appliance is plugged into a European outlet, there is a higher voltage than the American is used to along with the high American current. Current is increased and high current plus high current is dangerous, because it could start a fire.

Why do lightbulbs typically burn out when they are immediately turned on, but not when they have been on for a while?
When the lightbulb is just turned on it's cold, and cold is a factor that decreases resistance. When resistance is decreased, current increases and a high current breaks the old filament in the lightbulb. When the lightbulb has been on for a while it is hot which increases the resistance and decreases the current, and a lower current won't break the filament like the higher current will.

How does a fuse/circuit breaker protect your house?
A fuse stops the current flow when it (the fuse) gets to be a certain degree of heat, when too much current is drawn from the wall. When the current gets too high, the fuse will burn breaking the fuse, cutting off current flow to all devices, so the wires don't cause a fire. A fuse is only added to parallel or parallel/series combined circuits, because they each branch of the circuit is individually power sourced (what your house has). Too much current = hot = possible fire = dangerous

***Important equations 

I = V/R  (Ohm's Law)
current is measured in amps

P= IV
power is measured in watts

F = kq1q2/d^2
force is measured in N

Mousetrap Car

Mousetrap Car

My partner was Holt Mettee, and we worked very well together. The process was long, tedious, and frustrating but in the end we figured out how to correctly apply our physics concepts to the car. All our hard work paid off in the end, because we won our class race!

Our car went....

velocity = distance
                    time
              =    5
                  2.91
              =1.718 m/s
This time put us in 1st place for our class as well as out of all the classes!
             

This is our car!!

First, we built our body out of a mousetrap car hot glued onto a rectangular piece of wood. We wanted a stable body so the overall car would be stable, and not wobbly which would cause the car to drift to one direction more than another. 

Next we glued on our wheels. We put rubber bands around them to create a small amount of friction between them and the ground, thus giving the wheels something to grab onto. 

Newton's 3rd law --> car pushes ground back, ground pushes car forward. This is the force that is doing work on the car, and causing it to accelerate. 

The tricky part was making sure that they were straight, and parallel to each other.

We added styrofoam on either side of the wheels to keep the wheel steady while rolling. This insured that the wheel wouldn't wobble while rolling, thus that it wouldn't move in one direction more than another.

We added some electrical tape in between the wheels and the axis slot to insure more that the wheels wouldn't slide towards one direction more than another.

This is the axis. The axis goes through the metal holes, having little friction, allowing it to rotate. The wheels are glued onto the axis, so when the axis rotates it allows the wheels to rotate as well, while keeping them straight and parallel. 

The next part was to add a lever arm. A common misconception is that the lever arm increases the force, thus creating the car to go faster. In fact, the lever arm is increasing the distance and decreasing the force. The longer distance allows the force to act on the car for a longer period of time. 

This is where the lever arm attaches to the axis. One side of the pink string is wrapped around the axis (here), and the other end is connected to the lever arm on the other side of the car. 

When you pull the spring on the mousetrap back (and have it like so), potential energy is created, because this is where the power source for the car is. When I lift my finger, the spring will rotate back to the other end (where it initially was), the lever arm will follow it, the string will unravel as the lever arm rotates to the other side, and the unraveling string will cause the axle to rotate, thus causing the wheels to rotate and accelerate the car in the forward direction. 





1) How Newton's Laws apply to the Mousetrap car and how it works 

Newton's 1st law states, "An object in motion will stay in motion and an object at rest will stay at rest, unless acted upon by an outside force."
--> A car in motion will continue in motion unless a force pushes it backward (friction)
*Remember that we only like friction in this experiment when there is a little bit on the wheels. Everywhere else, friction is your enemy. 

Newton's 2nd Law states, (a = F/m)
--> Acceleration = force/mass
*big force = big acceleration
*too much mass = little acceleration 
*We want a small amount of mass with a big force. 

Newton's 3rd Law states, "Every action has an equal and opposite reaction."
--> Car pushes ground back, ground pushes car forward. This is the force that is doing work on the car and causing it to accelerate. 

2) Our wheels relied on friction due to Newton's 3rd law. We put rubber bands around them to create a small amount of friction between them and the ground, thus giving the wheels something to grab onto.
rough surface = more friction
smooth surface = less friction
... so we had to find the right balance between rough and smooth.
 *On the wheels was the only place that friction was our friend. 

3) In terms of wheels, Holt and I changed our wheels at least 100 times, because we needed to find the right balance for wheel size, so that we could cause a torque on the wheels. The body shouldn't have a torque, but the wheels need a torque to turn. The force of friction on the ground is what causes a torque. 
Bigger wheels = longer lever arm, but too much rotational inertia
Smaller wheels = not a long enough lever arm, and not enough rotational inertia.
Medium size wheels = a good size lever arm and the right amount of rotational inertia. 

4) The Law of Conservation of Energy states, "the total amount of energy in a system remains constant (is conserved), although energy within the system can be changed from one form to another or transferred from one object to another. Energy cannot be created or destroyed, but it can be transformed."
--> When the mousetrap is pulled back, there is potential energy built up before the trap is released. When the trap is released, the energy become kinetic energy, because kinetic energy is the energy of movement. 

5) Rotational velocity - the amount of rotation that a spinning object undergoes per unit time. The wheels have a rotational velocity.
Big wheels = large rotational velocity
Small wheels = small rotational velocity
Medium sized wheels = a medium/good amount of rotational velocity        
Rotational inertia - an object's resistance to rotate. 
The bigger the wheels the bigger the mass and thus the bigger the rotational inertia
The smaller the wheels the smaller the mass and thus the smaller the rotational inertia
Tangential velocity - the linear speed of an object moving along a circular path. 
*You want a large tangential velocity, which means the wheels are moving at a fast pace. 
*Remember that different sized wheels will have different tangential velocities (example: your car's wheels and your friend's car's wheels). BUT all the wheels on the same car with have the same tangential velocity, just different rotational velocities and rotational inertias, because each wheel is covering the same distance in the same amount of time.  

6) We can't calculate the instantaneous speed of the car (potential energy, kinetic energy, or force exerted from the spring) because the force of the spring isn't parallel to the axle spin, so work can't be calculated. 

Reflection 

1) Our final design was COMPLETELY different than our original. We were trying all the wrong things before any of the right. Our first model was using a cardboard tea box as a body, mason jar tops as wheels, and balloons as the power source. Our final model was using wood as the body, CD's with rubber bands as the wheels, and a lever arm as the source. The promotion of the changes was to test the car, fail, and try something different that would fix that current problem. We just kept encountering issues with the car and making small change after change until we finally applied the correct physics concepts to the car.

2) The major problems with our car was the wheels. They were always either uneven, not touching the ground, not parallel with the axle, or causing the car to drift to one direction more than another. This is why we changed them so many times, but then we figured out that our body was falling apart, thus not allowing our axles to be stable and parallel to each other. So we thought the problem was the wheels (which it was) but the body was also making a big difference in the movement of the car. Once the body was stable, the car started to respond a lot better.

3) If I were to make my car go faster, I would lighten up the body and even out the axles/wheels because I think they were still a little uneven. 

4) If I were to do this building process again, I would most definitely do more research. Holt and I just started gathering materials and building without any knowledge of which physics concepts to apply. We should have drawn a model to demonstrate how we wanted to use those concepts, before building the actual model. That would have speeded up the process a significant amount, because we spent a lot of time taking apart the model and rebuilding it.