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The mantra we repeat in our programs is “I may not know, but I know I can figure it out.” Our projects are designed to foster the same “we can do it” attitude, and we encourage you to share this message with your children at home.

6th-8th Grade Projects

Resource 1

Spin Art

Centripetal force is defined as, “the force that is necessary to keep an object moving in a curved path and that is directed inward toward the center of rotation,” while centrifugal force is defined as “the apparent force that is felt by an object moving in a curved path that acts outwardly away from the center of rotation. 

Our favorite example of centripetal force is a roller coaster! The feeling you experience during a roller coaster loop de loop is centripetal force! The track is exerting force outward on you and the car you’re in. This counters gravity which is trying to push you back down to Earth. 

Have you ever been driving in a car when someone makes a quick turn and you feel like you’re being pushed out of the car? This feeling is actually known as a centrifugal force. This is not actually a real force, but a feeling. When you take that sharp turn, it feels like you’re being pushed out of the car, but really the car is pushing on you to change the direction you’re moving in to make a turn, which is our centripetal force!

In class we explored both of these concepts by working to pick up bouncy balls with spinning glasses and keeping water in a cup as we swung it in circles around the room. 

In our spin art machines, the centripetal force acting on the system is supplied by the spinning motor. This force keeps the paint moving in a circular path while it is on. This is a “pull” force, similar to how satellites are kept in orbit due to the pull of Earth’s gravity. However when the motor is turned off that force is no longer pulling on the paint so it instead flies away in a straight line away from the circle’s center.

Check out our Rosie Explores activity below to learn more!

Rosie Explores Centripetal Force

Jump into this fun experiment while exploring rotation and centripetal force!

Resource 2

Zoetropes

Today we explored three concepts that work together to form the basis of the moving animations we see in our favorite cartoons and movies. Below are some definitions and a couple of questions to get your kids talking about the Zoetropes they created today.

  • Persistence of vision– refers to the length of time the retina (the “screen” at the back of our eyes which is sensitive to light) retains an image. If we see a light flash every tenth of a second or less, we perceive it as continuous. The impression of each flash of light remains, or persists, in the retina for at least one-tenth of a second. Because of this persistence, we can’t tell where one flash ends and the next begins. Instead, we perceive a continuous light.
  • Phi phenomenon– is a result of human instinct. Our brains strive to make meaning from what we perceive. When we see different images close together our brains quickly create a relationship between them. The phi phenomenon is the optical illusion of perceiving continuous motion between separate objects viewed rapidly in succession. 
  • Stroboscopic effect –  is a visual phenomenon caused by the distortion of an image that occurs when continuous motion is represented by a series of short or instantaneous samples. 

The slit in the persistence of vision scope, the slits in our zoetropes and the flipping between the pages of our flip books all work to create what is called the stroboscopic effect. This combined with persistence of vision and the phi phenomenon work together to make still images created by animators appear as fluid moving images.

Questions

  • Why wouldn’t your zoetrope work if it didn’t have the black paper? The image wouldn’t be flashed or “strobed”. The scanning of the slits keeps the pictures from simply blurring together, and the user sees a rapid succession of images, producing the illusion of motion.
  • What does your eye do when it sees an image? It retains a “picture” of the image for 1/10 of a second. Refer to the definition of Persistence of Vision above. 

If your kids want to create another animation strip they will need a 17 inch long and 1.5 inch strip of paper. They should space each still image about 2 inches apart from each other. 

Check out our Rosie Explores activity below to learn more!
Biology

Rosie Explores Persistence of Vision

Have fun exploring the persistence of vision by understanding how our eyes let us see!

Resource 3

BioMechanical Hands

Today we explored biomechanics (the study of the mechanical laws relating to the movement or structure of living organisms). Focusing on our hands, we examined the mechanics that allow us to grip and move objects. More specifically, we explored how bones, tendons and muscles work together. 

Using a stress ball we explored bone structure, identified where our joints bend, felt what muscles contract, and how our tendons help those three things work as one to squeeze the ball. 

Using that knowledge we then built our own “robotic” hands that can pick up a tissue paper ball and “throw” it across the room. 

Check out our Rosie Explores activity below to learn more!

Biomechanics a child's hand holding a biomechanics robot hand
Biology

Rosie Explores Biomechanics

Dive into biomechanics and learn how your hands work!

Resource 4

Edible Water Bottles

Today we explored how the body forms clots by experimenting with spherification to create edible “water bottles”. 

When the body is cut the body undergoes a process known as blood clotting to stop the bleeding. Blood clotting helps form a blood clot which works as a plug to fill any holes. How exactly is a blood clot made? When the skin tears, the body sends a message calling on special cells known as platelets. Platelets, which are already floating around in the blood, arrive at the wound and come together to create a barrier at the wound’s opening. This barrier slows the flow of blood, but platelets alone aren’t very strong. They need help from another special material known as fibrinogen proteins.

Fibrinogen proteins rush to the wound and, when they arrive, they change into fibrin fibers. Like string, the fibrin fibers help link and strengthen the platelets already plugging the wound. This process is known as coagulation and it’s a chemical change that helps turn liquid blood into a solid. In this case, the new solid is our blood clot!

In today’s experiment we combine two different chemical substances (sodium alginate and calcium lactate) to form our own version of a blood clot using water!

The link to the project video can be found here: https://www.rosieriveters.com/edible_water_bottles