Cycle 2 Week 21 Hands-On Science script for all ages - Towers, by Robyn Cooper Today we are going to think like engineers. Engineers use science, math, and even art to solve problems. Our problem is to build the tallest tower possible, that is also stable.

Before we start science today, let’s sing the scientific method. [Sing the song, to the tune of Pop Goes the Weasel. “The Scientific Method is Question, Research, Hypothesis, Experiment, Analysis (clap!) and conclusion.”

We are going to talk about building towers today.

Proverbs 18:10 says The name of the LORD is a fortified tower; the righteous run to it and are safe.

What’s our Question? How can I think like an engineer to build the strongest and tallest tower possible?

• Now, what makes a tower, a tower? Let the kids brainstorm. A Tower is a tall structure, taller than it is wide. It is a self-supporting structure that could house machinery, people, or operators, etc.

• How is a tower different than a building? They do not house many people, but buildings are often confused with towers, like the TWIN TOWERS in NYC that collapsed in September 11, 2001. They were buildings.

• What problems do towers solve? Let the kids brainstorm: • They allow someone to reach a great height to see over a great distance (watch tower, life

guard tower), • to reduce the interference of obstacles when sending messages through the air

(communications tower), • to enable something to be seen (clock towers, light signals), • to send harmful gases above creatures it could harm (chimneys), • to take advantage of potential energy (drop tower, water tower, elevator tests, diving board, • for art or symbols (tower of Babel)

• What do engineers need to consider when they are designing a tower? Tell kids, “Don’t answer this yet, we’ll come back to it.”

Let’s do our research.

There is just one main question to ask in our research:• What is the science of towers? But to answer this last question, let’s first think about what

kind of work does a tower have to do?

AND, before we think about the science of towers, I’m going to show you some ancient towers, and some more modern towers today. Look and see how God has enabled man to figure out how to make towers before any advanced machinery was around in ancient times, and how

those features are still used in modern towers. Man had to make use of SIMPLE MACHINES in ancient days.

OPTIONAL REVIEW OPPORTUNITY:

GIVE ME SOME EXAMPLES OF SIMPLE MACHINES AGAIN. (SEE BELOW).

DO YOU REMEMBER HOW THE EGYPTIANS USED SIMPLE MACHINES TO BUILD PYRAMIDS? WHAT SIMPLE MACHINE DID THEY USE? THE RAMP, ALSO CALLED THE INCLINED PLANE!

Towers have been used by mankind since prehistoric times. Look at these ancient towers and tell me what you think they have in common. (see below).

Ziggurate of Ur, 3rd Millennium BC by Sumerians

The Tower of Jericho is an 8.5-metre-tall (28 ft) circular stone structure, built in the Pre-Pottery Neolithic A period around 8000 BCE.[1] It is among the earliest stone monuments of humanity.[2]

Etemenanki, in Babylon during the 2nd millennium BC. Considered the tallest tower of the ancient world. Maybe the Tower of Babel. It no longer stands. It was a tower made for a

false god.

Some of the earliest surviving examples are the broch structures in northern Scotland, which are conical towerhouses, or round towers, and are preserved from the Iron Age. It is thought to have been constructed c. 100 BC, and is one of more than 500 brochs built in Scotland.

Most brochs were built in the period from 100 BC to 100 AD.

Now let’s look at a few more modern examples. What do they seem to have in common with ancient towers?

Eiffel Tower in Paris, 1887 to 1889. Leaning Tower of Pisa in Pisa, Italy built from 1173 until 1372.

Two Towers in Bologna, Italy built from 1109 until 1119

Okay, now we are ready to discuss the science of towers.

Engineers have to think about the science of towers. What force do you think towers are fighting every day?

Gravity! GRAVITY! Yes! Let’s go over our gravity facts again, just for review.

1. Objects with mass are attracted to each other, this is known as gravity.2. An object’s weight, does not impact the force of gravity on it, or its speed when it races to

the ground.

Yes, towers fight gravity… and something else… Force.

REVIEW OPPORTUNITY: NEWTON WAS A MASTER OF FORCE. HE DISCOVERED THAT FORCE = MASS X ACCELERATION. WHICH LAW OF MOTION IS THAT? 2ND! LET’S SING IT TOGETHER (TO THE TUNE OF HAPPY BIRTHDAY) “NEWTON’S SECOND LAW OF MOTION STATES FORCE EQUAL MASS TIMES ACCELERATION.”

Like bridges, towers face tension and compression caused by the weight of the materials the tower is made of, and anything resting on the tower itself.

REVIEW OPPORTUNITY, TELL ME WHAT THE FOLLOWING ARE: • COMPRESSION - (A PUSHING OR SQUEEZING FORCE, ACTING INWARD) • TENSION - (A PULLING OR STRETCHING FORCE, ACTING OUTWARD) • LOAD - (THE TOTAL WEIGHT OF THE BRIDGE AND THE THINGS IT CARRIES)

Now I’m going to expand your knowledge further, because towers fight some other forces. So, you can add a few new terms to your list:• Shear: A force that pushes in

opposite directions and causes it to bend on the inside, see https://www.youtube.com/watch?v=8PXcJ52PHuw

• Torsion: A force that twists… you learned about “Torque” in week 16 in my class in your Shape UP experiment where you rolled marbles and tape rolls down a ramp. It’s weight, or mass, was closer to its center of mass, so it had more torque. It took less gravity to pull it over and spin. So remember the ruler, who had more weight on one side? When I the center of mass was OFF, the ruler twisted and fell as its potential energy converted into kinetic energy.

Engineers think about how forces act on structures in 3 main ways.1. the force’s magnitude (how strong)2. its direction (where is the force pushing or pulling)3. the point and plane of its application (where is the force applied)

A tower is subject to: • wind pressure• vortex shedding (Newton’s 3rd law of motion), see https://www.sciencedirect.com/topics/

engineering/vortex-shedding • seismic disturbances etc (earthquake!)• If a tower is part of a suspension bridge (a pile), and it sits in the water, then water pressure is

a factor

Let’s start experimenting.

I have four towers here. Which do you think is strongest?

1. One has parallel sides. 2. The next is smaller as it gets taller. 3. The third is asymmetrical. 4. The fourth is smaller as it gets taller, but also is hollow in its center.

Why?

Up to a certain height, a tower can be made with the supporting structure with parallel sides. That looks like this (set up two straight tall building blocks).

However, above a certain height, the compressive load of the material is exceeded and the tower will fail. (keep building tall until the tower falls over).

This can be avoided if the tower's support structure tapers up the building. (now make the base wider and build upwards, showing the kids how you can achieve more height).

A second limit is that of buckling (starting to bend)—the structure requires sufficient stiffness to avoid breaking under the loads it faces, especially those due to winds. (blow on your tower).

Many very tall towers have their support structures at the periphery - the outside edges - of the building, which greatly increases the overall stiffness.

Now let’s do our experiment.

Let the kids start building towers with their families. They may even want to sketch their design on paper.

When you do your analysis at home, record how strong and tall you could make your tower, applying the pressure of wind (your breath), and earthquakes (shake the table). Design another structure if you want, and retest it. Go through the scientific method this way… Question, Research, Hypothesis, Experiment, Analysis (clap!) and Conclusion.” Try modifying the things in your tower:• Base width (lower the center of gravity)• Reinforcements on the periphery or outside of the tower• Symmetry• The slope of the sides of the tower (parallel or tapered, and HOW tapered?

We will run a campus contest on week 24 together. Families will compete using just one final tower design. You will be limited to straws and as much tape as you like.

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