Down to the Core


  • 1

    Here are some of the materials you can use

    • craft or popsicle sticks
    • flexible plastic straws 
    • paper cup (6-oz [170-ml] or larger) 
    • 1 pencil (sharpened)
    • 2 potato slices (1/2-in. [1-cm] thick) 
    • rubber bands 
    • skewers
    • small binder clips (3/4-in. [2-cm])
    • tape (duct or masking) 
    • 1 wide straw that the flexible straw can fit into (optional)
  • 2

    Prepare ahead of time 

    • Have paper and a pencil ready to write down ideas and sketches as you design.
    • Think about why scientists might be interested in collecting samples.
    • Pick up a slice of potato and push a straw through it. Look at the potato sample in the straw. This is a core sample from inside the potato.
    • TIP: Rock and soil samples reveal a lot about the chemistry, physical structure, and the ability to support life of a planet, moon, or asteroid.
    • TIP: NASA uses mechanical rovers to collect samples when they can’t send a person into space to do the job. A rover is a type of vehicle that can drive over land that’s rocky, dusty, sandy, or rough.
  • 3

    Think about the challenge

    • How will your device have enough energy to push into the potato?
    • How can you build a frame to hold the plunger, which is the part of the device that pushes into the potato?
  • 4

    Think about and write down ideas

    • Why do people gather samples? (Cooks sample foods; doctors sample human tissues; geologists sample rocks)
    • What will you use to guide the straw into the potato?
    • What will you use to stabilize, or keep steady, the thin straw as you slide it up and down?
    • TIP: Use a sturdy outer casing to keep the thin straw steady so it can slide smoothly up and down the frame. This is similar to how the outer casing of a push-pop ice cream treat keeps the ice cream steady as it is pushed out.
    • TIP: Inventors’ and engineers’ first ideas rarely solve a problem. They brainstorm, try different ideas, learn from mistakes, and try again––this is part of the design process.
  • 5

    Look at the materials 

    • How will you build a frame that can guide the straw into the potato?
    • What materials will you use to give your device the energy to drive the plunger into the potato?
    • How will you connect the plunger to the frame?
    • What will you use to hold the frame together?
  • 6

    Design and build the frame

    • Decide how you will build the frame.
    • Think about how it will guide the straw into the potato. 
    • Choose your materials and build the frame.
    • TIP: You might want to look at the barrel of a clickable ballpoint pen to help you think about how to guide the straw through the frame and into the potato. Notice how the barrel of the pen keeps the tip steady as it comes through the opening in the bottom.
  • 7

    Design and build the frame (continued)

    • Decide how you will build a crosspiece, or a rod that will sit across the frame and hold the plunger in place.
    • Build the crosspiece.
    • Attach it to the frame.
  • 8

    Design and build the plunger

    • Decide how you will build your plunger so you can grasp it and thrust it into the potato.
    • Think about how you will make it strong enough to go into the potato.
    • Build the plunger.
    • TIP: If you want to increase the plunger’s weight, or mass, try adding some binder clips. With more weight there is more potential, or stored, energy when the plunger is pulled back against the rubber bands. This allows the straw to do more work.
  • 9

    Design and build the plunger (continued)

    • Decide how you will create enough force so the plunger will go in the potato.
    • Attach the rubber bands.
    • TIP: To increase the force of the plunger, try adding more rubber bands. When you stretch the rubber bands, they build up potential (stored) energy. When you release the rubber bands, the potential energy changes to kinetic (motion) energy. When the straw hits the potato, the kinetic energy changes to mechanical energy and does work. The more potential energy the plunger has, the more deeply the straw can penetrate and do more work.
  • 10

    Test your plunger

    • Test your device. 
    • Send your plunger into the potato.
    • Pull out the sample. Modify your design if the plunger does not go into the potato.
    • TIP: If the straw bounces off the potato, try to strengthen the straw by sliding something inflexible into the wide straw, such as a thin skewer. Secure it to the plunger so it thrusts into the potato along with the straw.
  • 11

    Collect your core samples

    • Collect your samples.
    • Position your plunger over the potato slice.
    • Pull back on the plunger.
    • TIP: If the straw doesn’t move up and down with the plunger, try taping it to the craft sticks.
  • 12

    Collect your core samples (continued)

    • Release the plunger and thrust it into the potato.
    • Collect your samples.
    • TIP: If the straw tip bends or breaks, try snipping off the broken end or use a new straw.
    • TIP: If the plunger doesn’t have enough force to enter the potato, try stretching the rubber band more. When you stretch a rubber band, you increase its stored energy, or its potential energy. When you release the rubber band, its potential energy is turned into kinetic energy, the energy of motion.
  • 13

    Did you know?

    • NASA Explores Space
      Osiris Rex is a spacecraft that will collect samples from asteroids. It uses a tool similar to your corer. Scientists study asteroids to learn about what the solar system was like when it formed five billion years ago. Osiris Rex will launch in 2016, with samples returning to Earth in 2023. Think about becoming a NASA scientist and you could do research with these samples!
  • 14

    Try this next!

    • Gather samples from different fruits. Modify your corer so it can get a core sample of a different vegetable or fruit.
    • Push the sample out. Invent an easy way to remove the sample from the straw.