NSW Syllabuses

# STEM Stage 3 – Activity 1

### Rube Goldberg inventions

A Rube Goldberg invention is a device or set up that is deliberately over-engineered to perform a simple task in a complicated way. They generally involve chain reactions.

The timing is flexible.

#### Description of activity

Students use materials provided to design and make a machine that performs a simple task and fits a certain criteria, eg there must be at least three transfers of energy.

#### Context

Students understand that forces affect movement and that energy can be transferred from one object to another. Students have been investigating simple machines. They will apply their engineering skills and an understanding of simple machines. The machine can include a combination of simple machines including a screw, wedge, pulley, inclined plane, lever and wheel and axle. In the final demonstration of the design solution, the students are only allowed to touch the machine once to start it.

#### Outcomes

Skills

ST3-5WT plans and implements a design process, selecting a range of tools, equipment, materials and techniques to produce solutions that address the design criteria and identified constraints
ST3-4WS investigates by posing questions, including testable questions, making predictions and gathering data to draw evidence-based conclusions and develop explanations
MA3-1WM describes and represents mathematical situations in a variety of ways using mathematical terminology and some conventions
MA3-2WM selects and applies appropriate problem-solving strategies, including the use of digital technologies, in undertaking investigations
MA3-3WM gives a valid reason for supporting one possible solution over another

Knowledge and understanding

MA3-9MG selects and uses the appropriate unit and device to measure lengths and distances, calculates perimeters, and converts between units of length
MA3-16MG measures and constructs angles, and applies angle relationships to find unknown angles

#### Resources

• Pulleys, wheels and axles, which can be easily made with cardboard and straws
• Construction equipment: tape, cardboard, paper towel and toilet paper tube inserts, blocks of wood, dominoes, car tracks, balls, marbles, toys, cups, etc

#### Work, health and safety

Check relevant Work, health and safety guidelines.

#### Evidence of work for assessment purposes

• A visual record of the machine – photo (top view and side view) or video of the working invention
• a labelled diagram showing modifications needed to enable the machine to work.

#### STEM teaching and learning activities

• Students identify and explore the uses of simple machines including a screw, wedge, pulley, inclined plane, lever and wheel and axle.
• Students research other Rube Goldberg inventions in order to understand the requirements of this task. See Managing a process of design and Carrying out a design plan.
• Students draw a plan of a Rube Goldberg invention that will fit the criteria, eg at least three transfers of energy. This design plan should indicate materials required, lengths, heights, positions and angles of placement. Some students may develop a scale diagram.
• Students determine and collect the materials that they will need to use to construct their invention.
• Students make their invention.
• It is unusual to make a perfect working machine on the first try. Repeat attempts at modifications are encouraged, should be noted and failures celebrated. It is through the failures and resulting modifications that students learn. These modifications should be noted on their original design plans with annotations explaining why the changes were made.

#### Vocabulary list

Force – a push, pull or twist
Friction – a contact force, objects touch
Gravity – a non-contact force that attracts objects to the centre of the earth
Energy – causes change
Kinetic energy – the energy in moving things
Transfer of energy – energy can be transferred from one object to another
Energy transformation – energy can change from one form to another, eg kinetic (movement) energy to heat energy
Efficiency – how effectively energy is transformed

#### Key inquiry questions

How are you going to record the details of your structure so that you or someone else can build it?
Scaled diagrams or diagrams with measurements of each component are the most accurate. Looking at a top view and a front view would be the most descriptive. (Application of the mathematical skills inherent in ST3- 3D & 2D Space 1 & 2, Angles 1 & 2, Position)

What information would be important to make this an accurate record?
Examples include length of runs, angles of elevation, position of objects and details above.

What effect does increasing or decreasing the slope have on the energy of the moving object?
Increasing the slope (angle of elevation) increases the amount of energy (gravitational potential energy) in the object. The more energy the object has, the faster it will go. The stored gravitational energy will be transformed into kinetic (movement) energy.

Why do moving objects slow down? What force(s) do you think is making it slow down?
Moving objects have kinetic energy. If some of this energy is transformed into heat energy through friction or sound energy, eg rattling, the amount of kinetic energy is reduced. Therefore the object will slow down.

What is happening to the energy in these cases?
The kinetic energy is changing, or is being transformed, to other forms of energy. Some energy may be transferred to other objects, eg when a rolling ball hits a domino and it falls hitting another domino. Energy is not lost; it changes from one form to another.

Not all these different forms of energy are useful, eg a rusty bike chain will cause a lot of friction. The friction will make the chain and wheels heat up. This means that the energy the rider puts in is not fully transformed into kinetic energy of the wheel. The energy lost through heat makes the transfer of energy less efficient. One can reduce the effect of friction by making sure that the bike chain is clean and well oiled. The bike therefore becomes more efficient because less energy is transformed into wasted energy.

Where are the energy transformations (changes of form) occurring?
Whenever there is a change of height, friction or sound. When there is a change of direction of movement, a force is applied in order to change the direction of movement. The energy needed to apply that force may be transformed into sound or heat energy.

What factors could stop or minimise the workings of the machine?
The factors are generally friction (which transforms kinetic energy into heat energy) and the transformation of kinetic energy into sound energy. Minimising friction and sound and ensuring that there is enough gravitational potential energy (height) will continue the movement.

The following statements outline some common preconceived ideas that many students hold, which are scientifically inaccurate and may impede student understanding.

That 'energy' and 'force' are the same thing
It is energy that is transferred to apply a force.

An object at rest has no energy
The amount of energy an object at rest may have can be determined by its position (gravitational potential energy), its chemical composition (chemical potential energy) and its shape (elastic potential energy).

Things 'use up' energy
The energy is never used up (law of conservation of energy), but it can change from one form to another (transformation of energy) or be transferred to another object.

If energy can never be 'used up' why do we need to conserve energy?
This refers to energy sources, eg coal or oil, which possesses chemical potential energy. Once coal or oil is burned, this chemical potential energy is transformed into heat energy and there will be no more coal or oil.

An object at rest has no forces acting on it
An object at rest, eg an apple on a table, has a number of forces acting on it – gravity pulling the apple down and an equal and opposite force from the desk pushing the apple up. Therefore the apple does not move until another force is applied to it, thus unbalancing the forces.

Large objects exert a greater force than small objects
The force on an object does not depend on its size; it depends on its mass (weight).

There are only two types of energy:

• kinetic energy – the energy of movement including heat, sound etc
• potential energy – stored energy including gravitational and chemical.

#### Support materials

YouTube video: How to make a simple Rube Goldberg Machine
YouTube video: Rube Goldberg Machine Contest 2014 winner
YouTube video: OK GO – This Too Shall Pass

#### Adjustments for the diversity of learners

Can you improve the speed at which your machine completes its task by changing a part of the engineering design?

How can we improve the efficiency and effectiveness of the machine by making some mathematical or engineering adjustments?

Identify aspects of engineering which have led to machines that improve the quality of life.

Describe coordinated actions of the body when performing gymnastic sequences or playing sports in terms of energy transfer, transformation and efficiency.

#### Review

In this STEM activity, your students have investigated the conservation of energy incorporating the First Law of Thermodynamics that:

• the amount of energy in a system remains constant
• energy is neither created nor destroyed, it only changes from one form to another.

Your students will further develop this concept in Science Stage 4 and Stage 5 and Physics Stage 6.