## MEDIEVAL ENGINEERS: THE SCIENCE BEHIND THE CATAPULT

A
catapult is a lever, a stick or beam, propped up by a fulcrum, the pivot point.
The catapult magnifies your force to throw an object. So, you do not need as big
of a force to propel a large object, but the larger the force, the farther it
goes. In ancient times, catapults were used to throw heavy rocks.

Levers
and fulcrums can be used to pick up heavy things like rocks and building
materials. Have you ever used a see-saw? That’s a lever and fulcrum! See if you
can point out which part of your catapult is the lever, and which is the
fulcrum? The craft stick with the spoon is the lever and the stack of other
craft sticks is the fulcrum. The spoon beam pivots around the stack to generate
the force to launch the load. When you press down on the spoon, it pulls up on
the rubber band on the opposite end—this is its potential energy. When the
spoon is released, it pulls back up on the rubber band and the pom pom goes flying!
The potential energy is converted into energy of motion- kinetic energy.
Gravity also does its part as it pulls the object back down to the ground.

Take
it Further:

Try
launching a bouncy ball with your catapult. Compare it with the pom pom. How far
or high did it travel? Did it go as high or far as the catapult?

The
catapult also demonstrates Newton’s 3 Laws of motion:

An object at rest stays at rest until a force is applied, and an object will stay in motion until something creates an imbalance in the motion. (First Law) The acceleration produced when a force is applied depends on the mass of the object. (F = Ma; Second Law) Every action causes an equal and opposite reaction. (Third Law)

The
pom pom will remain at rest until a force acts on it (the release of the spoon
and/or gravity) – First Law

The
bouncy ball will not travel as high or far as the pom pom as the bouncy ball
has more mass than the pom pom and will require a larger force to travel the
same distance and speed as the pom pom – Second Law (Force = Mass X
Acceleration)

When
the spoon is pushed down, the load (pom pom or bouncy ball) travels upward- in
the opposite direction equal to the force applied on it. (Third Law of
Action-Reaction)

A catapult is a simple machine that has been around for ages. Have your kids dig up a little history and research when the first catapults were invented and used! Hint; check out the 17th century!

## EIGHT-LEGGED ENGINEERS!

If you are not a fan of spiders, you are not alone. Before you push away another spider web, remember this: relative to weight, the strength of a spider web rivals steel and Kevlar, the material used to make bullet-proof vests.  Its incredible, pliable strength has inspired scientists to develop a surprising number of products—but it is just one of the amazing things that may give even arachnophobes a new appreciation!

Here are 3 Fun Facts:

1. SPIDER SILK TRANSFORMS FROM LIQUID PROTEIN TO SOLID THREAD WHEN IT LEAVES THE BODY.

Spiders are like tiny silk production factories. Inside their bodies, thread is stored as a highly concentrated liquid. A common garden spider can produce as many as seven types of silk, each made up of a different sequence of proteins. Each type of thread serves a distinct purpose: one, for example, makes the web stretchy to better absorb the impact of insects smacking into it; another makes the thread less brittle. Still other proteins protect the threads from bacteria and fungi and keep it moist.

2. SPIDERS USE THEIR SILK FOR MUCH MORE THAN CATCHING DINNER.

Webs are used for trapping prey, but spiders produce silk for other reasons, too. Hunting spiders often make silk to use as drag lines extending more than 80 feet—across rivers and lakes. By building their super-strong web across the water like a bridge, they can catch large insects like dragonflies that quickly swoop and rise along the water’s surface.

3.WE LOOK TO SPIDER WEBS FOR ALL KINDS OF USEFUL PRODUCT IDEAS.

Because spider silk is so flexible, light, strong, and water resistant, it presents numerous product possibilities.  Researchers are busy developing bioinspired, synthetic versions of spider silk like “liquid wire,” as well as adhesives based on their sticky glue-like protein droplets. Taking inspiration from spider silk, researchers have recently made big strides in designing medical devices, parts, and supplies that need to be strong and stretchy or sticky. These include artificial tendons, ligaments, and implants, as well as sutures, adhesives, and bandages.

Learn more about spiders by participating in our HTHT @ Home Science Experiment: