Name: Bridget Sullivan

Name: Bridget Sullivan Date of Lab: November 9th - November 15th, 2007 Date Due: November 20th, 2007

Title: Balloon Car Lab Report

Question: What materials and designs will make for the most successful balloon cars?

Hypothesis: It is hypothesized that cars that are built with lighter and more aerodynamic materials will go further due to a lesser amount of friction and air resistance.

Independent Variable: The materials and the design of the car

Dependent Variable: The success of the car, or the distance that it travels

Materials:

- Balloons ($ 1.85 * 2)

- CD’s

- Straws

- Knitting Needles

- Styrofoam Insulation

- Duct Tape

- Cardboard

- Plastic Pencil Holder

Procedure:

1. Students build a car powered by a balloon that will travel as far as possible.

2. Students must test their cars and record their data, as well as class data.

3. Students will analyze the class data in order to assess what materials and

designs make for the most successful balloon cars. Data:

Greatest Mass of Greatest Mass of Distance Car Distance Car Student Name (meters) (grams) Axels Student Name (meters) (grams) Axels Stenstrom, Dalton 5 92Axels turn Fyfe, Bethany 18 102 Axels Turn Neilson, Dan 9 40Axels turn Berke, Josh 18 79Wheels turn Lorden, Caroline 8 210Axels turn Sullivan, Bridget 3 89Axles Turn Howard, Hailey 7 124Axels turn Ward, Rachel N/A 40Wheels turn Walsh, Brittney 6 88Axels turn Thyng, Heather 5 93Axels turn Craggy, Ethan 4 81Wheels turn Johnson, Sandy 0 110Axels turn Blinn, Korissa 3 91Axels turn Morrill, Francis 0 303Wheels turn Reed, Stephen 6 125Axels Turn Tulley, Corbin 17 87Axels turn Landry, Eric 18 122Axels turn Gallant, Cody 18 171Axels turn

Calculations:

Mass of balloon Cars

10 9 8 s

r 7 a C

r 5 e b 4 m u

N 3 2 1 0 Sucess ful Cars Less Unsucessful Cars Sucessful Cars More Unsuces sful Cars than 100 gram s Less than 100 gram s than 100 gram s More than 100 gram s Mass Wheels of Balloon Cars

10 s r

r 6 e b m

0 Axles Turn On Wheels Turn on Axles Turn on Wheels Turn on Sucessful Cars Successful Cars Unsuccessful Cars Unsuccessful cars Wheel Type

Analysis:

1. Newton’s First Law of Motion states that “…an object in motion will stay in

motion and an object at rest will stay at rest unless acted upon by an outside

force”. The force that acted upon my stationary balloon car was the air exiting

the balloon. This force caused my car to begin to move. The car because it

was stationary wanted to remain unmoving, but because the force of the air

was stronger than that of the force keeping the car in place, the car

accelerated. These same ideas also cause the car to stop moving. As the car is

accelerating, it is picking up more and more air resistance, a type of friction

that resists motion. Eventually the car reaches a point when there is little to no

air left in the balloon and the air resistance and force of gravity out balance

the force of the air from the balloon, thus causing the car to stop. 2. Newton’s Second Law states that “…Force is equal to the objects mass

multiplied by its acceleration, or F=ma”. The mass of the car plays a very

important role when the car is moving. This is because mass times the

acceleration equals force. The greater the mass or acceleration, the greater the

force. This also has to be evenly balanced, because if the mass is too large the

acceleration will be slower. This law of motion affects the car predominantly

at the start. The mass of my car was 89 grams. Because you can switch around

the equation to find the value of F, M or A the mass is very important. Force

divided by the mass gives you the acceleration. If you want a high

acceleration rate, you need to be sure that your mass is very low. If your car

has a very high mass, your acceleration will be low causing your car to run out

of air in the balloon (force). The balloon is the set force. It is about the same

for every car. It is the air expelled from a twelve-inch balloon. This is

something that you can change, but you can change the mass to get a higher

acceleration.

3. Momentum is an objects mass multiplied by its velocity. Velocity is the

acceleration of an object in a certain direction. Because the mass is a part of

the equation for momentum in order to have a good momentum to keep your

car in motion, even when the air has run out you need to have the correct

balance of velocity and mass. You want to velocity to be a high number

because velocity refers to speed and if your car goes fast, it will cover more

ground faster. You also want the mass to be high to have a good momentum,

but you have to remember that while a greater mass means greater momentum

it also means a decrease in acceleration. This is why the perfect balance is needed in order to have a momentum that will keep your car going even when

the air in the balloon has been depleted.

4. Newton’s Third Law of Motion states that “…For every action there is an

equal and opposite reaction”. To relate this to the balloon cars you must first

figure out what the first object is and what it is acting on. In this case, the first

object is the air exiting the balloon and the object that it is acting on is the

balloon, which is attached to the car making them one. This is similar in

concept to the idea of wearing a seat belt. It makes you a part of the car the

same way the duct tape that I used to attach the balloon to the car makes the

balloon a part of the car. The second object is the car/balloon and the object it

is acting on is inside of the balloon, pushing outwards. This means that while

the air from the balloon is being expelled exerting a force backwards, the car

is exerting a force in the equal and opposite direction causing it to accelerate

forwards, just like the example of the squid in our textbook (pg. 333). This

greatly affects the motion of the car because without the reaction force from

the car, the car would not move. You cannot have one, without the other. The

force in this law, in this case the air from the balloon relates to Newton’s First

Law because an outside force is needed to move an object that is at rest, and

the balloon car is at rest when it starts and the balloon is the outside force

acting on it.

5. The three different types of friction are: Sliding Friction, Rolling Friction, and

Fluid Friction. They are all related to the design of my balloon car because

they are all present and opposing motion while the car is moving.

The rolling friction is present because the wheels are rolling over the ground. This type of friction is present throughout the test. The strength of rolling friction depends on the types of surfaces being pushed together and how hard they are pushing together; these are the same variables that affect Rolling and Fluid

Friction. The two types of surfaces that were pushed together were the ground (in this case tile) and the wheels (in this case CD’s). There was no way for me to measure how hard they were pushing together so, this factor does not apply to this situation. Because the CD wheels were very thin and narrow, they had very little contact with the ground, resulting in a very small amount of rolling friction.

Looking at Fluid friction thought, there is much more. This is because air resistance is a type of fluid friction. There are two factors that affect air resistance and they are: surface area and velocity. The greater the surface area and velocity of your car, the greater the air resistance. A greater velocity is a good thing, in that it allows your car to go further in less time, but it also increases the air resistance, which slows you down. This is why you need to have an aerodynamic design. The surface area also affects air resistance. This is where the aerodynamics of your car come into play as well. If you have a well-designed car with as little surface area as possible, you will greatly decrease the air resistance allowing your car to travel much easier.

The sliding friction that is present on my balloon car is in between the axles and the straw that they sit in. This is where the highest and strongest amount of friction occurred. Sliding friction is when two objects come in contact with one another and one slides over the other. This is exactly what was happening in between the axles and the straw and is one of the main reasons that the cars did not go as far as it potentially could have. This friction affected my car most when it was traveling a distance because, friction resists movement, and the axles need to spin in order for the car to move. All of these Frictional forces affected my car at the end, when it came to a

stop because they over powered and created an imbalance between the frictional

forces and the force of the balloon. This is what caused the car to stop.

Conclusion:

In this investigation, it was investigated which materials and designs would make for the most successful balloon cars. In short, each student built a balloon car out of materials that they found around the house. While all of the balloon cars were very different, the students had only two choices when it came to attaching the wheels. The wheels could either spin on the axle or have the axle spin. It was originally hypothesized that that cars built with lighter and more aerodynamic materials would go further due to a lesser amount of friction and air resistance. The data does support my hypothesis, because the cars that were successful, or went greater than ten meters, had very aerodynamic designs and were built of lightweight materials such as straws and balsa wood.

The successful cars went on average about 17.8 meters this distance can be directly related to the design and materials of the car. All of the successful cars were very streamlined, having less surface area, which decreased the amount of air resistance on the car. In class, we watched the movie “Fast Cars” and it was all about the need for a car that had a shape that would allow the air to travel over it and create little to no drag. This is why the cars that were successful worked so well.

The unsuccessful cars, or cars that traveled less than 10 meters, traveled on average 3.07 meters. This is not a successful car, in part due to the designs of many of them. Many of the designs were large and bulky. This meant that there was a lot of surface area, leading to an increased amount of air resistance. Because many of the cars were very bulky, they also had a greater mass. This means that the cars had more inertia, meaning that they are much harder to accelerate than an object of a lighter mass. This is true because if you refer back to Newton’s First Law, or The Law of

Inertia, it states, “an object at rest will stay at rest”. This is why the object is hard to get moving when it has a greater mass.

This project greatly enhances student leaning of topics discussed in class such as:

Newton’s Laws, the Concept of Momentum, and Friction. It is also an example similar to the water relay; it has the same concept of Newton’s First Law, in addition to the rest of the laws and the topics mentioned above. It goes into much greater detail than the water relay, yet gives some of the same basic information giving students two ways to comprehend the information. This project also shows air resistance through a “real world” application, as opposed to just watching a movie on air resistance. With the balloon car, we can actually see that little things that we change can make enormous differences in the functioning of our car. In all this project was a great learning experience and allowed me to see the forces and how they worked to my advantage and disadvantage, and I think that others will say the same.

Error Analysis:

There were many ideas that I tried that did not work. One of them was having the wheels spin rather than axles that turn. It is very difficult to create wheels that spin and that are straight enough and sturdy enough so that they do not wobble. When they wobble, they are in contact with the ground in such a way that creates more rolling friction than normal. This rolling friction is the second strongest type of friction and can slow your car down a lot. This is why it is so important to make sure that everything is tight, as it said in the movie “Fast Cars”. If things are not tight, there is excess friction and air resistance to name a few, and the car travels in a state that greatly decreases the reliability and success of the car. Another idea that did not work was having a very tall car that was bulky. This is because it created a lot of drag, or air resistance, due to the excessive amount of surface area. This is true because surface area is a factor that affects the amount of air resistance on an object. A third design that did not work well was using a straw to direct the flow of air from the balloon. The air needs to be able to freely come out of the balloon at the correct speed so as to create a force that is strong enough to propel the car forwards. When the straw was in the balloon, the opening was not large enough and was not letting enough air out to propel the car, so it did not move. Although many of my ideas did not work well, with help from my dad, we were able to figure out a few that did work.

When I redesigned my wheels, I made them so that the axle spun inside a straw and the axle was firmly hot glued to the wheel so that the axle was the only thing that spun. This worked out surprisingly well. I think that it worked because the wheels were very straight, allowing for minimal ground to wheel contact, reducing the amount of rolling friction. In addition, because friction resists movement, the less friction that is present, the faster, and further the car goes. Creating a car that was more of a frame than a box, also worked very well. This made it so that the only thing that was causing a lot of air resistance was the balloon itself and that was a factor that everyone had to work with. With a very sleek body of the car, there was less air resistance resulting in less drag allowing the car to travel through the air without experiencing any type of fluid friction. One other adjustment that I made to my car that worked well was securely attaching the balloon to the car, using duct tape. The duct tape attaching the balloon to the car acted in the same way a seatbelt would act on a person. It makes it a part of the car. This is beneficial because if the balloon is not securely attached it could become loose and fall off, resulting in a low travel distance for your car. Attaching the balloon well was an adjustment that allowed my car to travel much further than it did the first time that I tested it.

This project was very difficult for me, because building things with my hands is not my strong point. I can understand how everything works; friction, air resistance, gravity; Newton’s Laws, etcetera. However, it is very difficult for me to put them into action. Having said this I think that the most valuable thing that I have learned from this project is to really think outside the box and ask for help. Even if that person is someone you would never normally ask, because chances are if they are not so good at the actual writing and that kind of school work then the will excel in the hands on projects and activities like this one. I also learned that if I ever want to take physics, then I better learn how to think mechanically and outside the box, if I wan to pass the trebuchet project. In all I think that this is a very valuable learning experience and now I have completed it, I am really glad that it was assigned.