Calculating Kinetics of a Student Designed Machine

This activity is designed for students to use critical thinking to design a working machine.

This activity is designed for students to develop their mechanical skills by building a machine.

This activity is designed for students to manipulate real-world objects to calculate quantities that describe those objects.

Key concepts: Develop an understanding of Kinetics and how it relates to an object's energy.

Vocabulary Words: Velocity, Acceleration, Force, Kinetic Energy, Potential Energy, Force diagram

This activity is appropriate for all students in Physical Science or Physics. It works best with smaller class sizes because of larger amounts of physical space necessary, both during the project and also for storage purposes. This is a unit long project that should be started before the unit of motion. While students learn about motion, they can go back to their projects and test various components of their project for those concepts. Construction tools will most likely be needed, such as hammers, nails, screws and screwdrivers, etc. However, no powertools should be necessary. Students should have a basic understanding of velocity and gravity. This activity could easily be teamed up with an economics or writing class for purposes of the engineering manual.

Overview:

Rube Goldberg Machine:

Students will work as individuals or groups to create and construct a complex, multi-step machine to complete a rather mundane task. Upon completion, each machine will be tested in front of the instructor, who will inspect the machine to insure that it falls within the required parameters set down at the beginning of the project. Students will also be asked to create an engineering handbook and maintain a budget to help them calculate the total cost needed to produce a single machine if their design was meant for production.

Introduction:

This project will likely fit best during or at the end of a mechanics unit as it relates to kinetics and energy. It could easily be made into a business-like venture in which student teams represent their own personalized company that has been hired to create a unique method for solving a mechanical problem.

Materials Needed:

- Building materials (scrap wood, PVC, string/rope, cardboard, paper , etc.)
- Simple Tools (hammers, nails, screwdrivers, sheers, sandpaper, etc.)
- Recording materials (stop watches, metric measuring tools, video recorders, motion detectors and software such as LoggerPro, etc.)

It is important to note that this is not an exhaustive list and not all of these components are required. In fact, it is rather easy to improvise using an assortment of materials and recording methods. Students can be responsible for providing their own materials. In fact, several businesses may be willing to give scrap materials to students working on a project, especially if students have a signed letter from the instructor describing the project they are working on in class.

Detailed Student Activities:

- Students will design a machine that has multiple steps/parts that can complete a task, but falls within a range of specific parameters.
o The number of steps can be determined by the instructor depending upon grade level and ability, but have a minimum of at least 5 distinct steps as part of the machine to encourage creativity and in-depth problem solving. The instructor can decide on whether or not these steps must occur in a linear fashion or if different steps occurring in parallel is acceptable.
o Common tasks that machines must complete could be any of the following:
Raising a flag a specific height, putting out a candle, moving an object a minimum (or specific) distance, launching a ping-pong ball at a target, etc.
o Machine parameters that students must follow could be anything from size minimums and maximums, weight minimums and maximums, cost, etc.
- Students will compile an engineering guide that gives the following:
o Calculate the potential energy at the initial stage of each step of the machine.
o Calculate the velocity of moving parts (linearly moving objects would be easiest, such as rolling marbles)
o More advanced students may try to tackle calculating torques and rotational motion.
o Step-by-step guide to building the machine, including pictures of parts and pictures of the machine after every couple of steps of production.
Having instruction manuals for putting things together as examples will be very helpful for students at this step. One can also do a simple exercise where students write directions on how to make a peanut-butter and jelly sandwich for an alien life form, where the instructor plays the role of the hapless alien.
o Detailed drawings or pictures of the completed machine from multiple angles.
o Force diagrams showing all the relevant forces for each step of the machine, including gravity, friction, tension, etc. These could be in addition to the pictures/diagrams of each step of the machine or could be added directly to the machine pictures already produced.
o Trouble shooting guide of what to do if certain steps don't seem to be working
Just remind students about what they struggled with when trying to get the machine to work and how they fixed those problems.
o Detailed cost analysis
Line-by-line cost of each component if students bought each item individually.
Estimated labor costs given a specific hourly wage




Closure Strategies:

- Students will brainstorm in their groups ways they could have improved the performance of their machine without drastically changing any of the steps.
o For instance, if a marble rolling down a ramp to knock over a domino is one step, if this step didn't work well (or even if it did), what could students modify to ensure that this step would work properly almost every time.
o Another angle on this would be to have students suggest what might not work as well if they made specific changes to a step of their machine that seemed to work perfectly.
o Also, students could predict how minor changes on individual steps might have impacts on other steps of their machine.
- Students will brainstorm in their groups ways they could reduce the cost of their machine, but still maintain its ability to successfully complete the task.
o Suggest changes in building materials, streamlining the time it takes to produce a machine (labor costs), etc.
o Also, students could predict how changes on individual steps might have impacts on other steps of their machine.

Teaching Notes:

Time Requirements:

This is a rather time consuming project. The best fit would be to start this project fairly soon after beginning a kinetics unit. It may be easier to have the machines finished near the beginning of the unit so that they can be tested for specific qualities (velocity of moving parts, energy, etc) as those ideas are taught in class. Give work time in class at least once per week. It can be pretty easy to tie in some key concepts from the current week and create a mini-lab in which students calculate some kinetic motion using a technique that would be valuable for them on their machines. For example, it might be useful to create a lab about velocity and acceleration of moving objects and then on one of the project work days have students calculate those quantities for each step of their machine using the techniques acquired in class.

Safety Precautions:

Since the construction of these machines will likely require tools of some sort, it is highly recommended that students only use non-power tools, unless you have experience with power tools in the classroom. It may also be prudent to supply the tools or ask the industrial arts rooms for some tools to borrow so that students do not have to bring items to school that may inadvertently be mistaken for weapons.

Also, make sure there is plenty of space for students to move around. This will minimize the common accidents of someone knocking something or someone over.

Tips for Success:

- Make the task that needs to be completed fairly easy. Students often add their own complexities to the machine, which usually makes the task more difficult to solve.
- Allow as much group collaboration as is prudent. Let students examine other machines and how those groups are tackling a specific problem, but try to limit flat out copying.
- Answer as many questions as you can with questions of your own. For example, if a student asks why a step of their machine always seems to fail, ask them something like, "Is it the whole step that fails or is their a specific component of that step that seems to cause the problems? What are some variables that you could change in this step that might make it work better?"

Individuals from each group will be "interviewed" regarding their machine. Each person will be asked a question about their machine regarding some aspects of calculating a kinetic quantity.

Students will also be turning in their engineering guide.

Also, students will receive points based on the success of their machine to achieve the given task.

I.B.1- design and complete an experiment
I.B.3- applying mathematics
I.B.4- identifying sources of error and their effects
II.C.1- potential energy
II.C.2- Potential vs. kinetic energy
II.D.1- Newton's Laws of Motion
II.E.2- Identifying forces