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Combine life science and physical science in this explosive activity
Combine life science and physical science in this explosive activity
Engage students with the short plant dispersal videos below. Allow students to Explore the concepts of kinetic and potential energy using one or both of the tabletop activities. Ask students to Explain how explosive seed dispersal works based on their new understanding from the tabletop activities.
Plant: Orange Jewelweed. From: Andrew Martin.
Plant: Squirting Cucumber. From: Smithsonian
Plant: Harry Bittercrest. From: Schel Sullivan
Plants have unique seed dispersal methods
Plants have unique seed dispersal methods
ENGAGE
What are the different ways plants disperse seeds?
Use this time to think of as many methods as you can. Your answers might include some of the following:
Transported by ground animals, like what squirrels do with acorns.
Carried by the wind, like dandelion seeds in the breeze.
Hitching a ride on animals, like ragweed seeds do with its Velcro-like burrs.
Falling to the ground, like a overripe fruit on a wild vine.
Carried by water, like the seeds of a mangrove tree.
Have you ever considered using the terms explosive or ballistic next to seed dispersal? That is exactly how some unique plants spread seed. Often, a slight vibration on the seed pod causes an irreversible explosion of seeds in all directions.
Use the animated pictures to the left, or the associated YouTube video, to discuss what it means for a plant to be explosive.
What types of force do you think are exhibited?
Tension and pressure are the two main forces that students may identify.
EXPLORE
Use one or both of the activities below to explore the concepts of potential energy and kinetic energy. Notice that in both the cobra weave and the catapult, the systems contain potential energy and that the potential energy is converted into kinetic energy when the system is released or activated.
Craft Stick Cobra Weave
Craft Stick Cobra Weave
Source: Instructables
Materials: Tongue-depressor-style craft sticks. (Popsicle stick-style also work but are less flexible and therefore more difficult to position).
Tongue depressors woven together using the cobra weave results in the buildup of tension, which is a form of potential energy. Once the weave is released by pulling the end tongue depressor, the potential energy turns into kinetic energy as the tension of the tongue depressors cause the weave to explode.
Craft Stick Catapult
Craft Stick Catapult
Source: Instructables
Materials: Craft sticks, rubber bands, plastic spoon.
Note: You can either glue a cup to the end of the catapult or rubber band a spoon to the end.
Use this catapult to experiment with potential and kinetic energy. What happens when the catapult is at rest? What type of energy is present when the arm is pulled back? What type of energy is present when the arm is released?
Once students explore the cobra weave or the catapult, ask students to Explain how the two activities are similar and different to the exploding plants they viewed earlier.
Ask students to elaborate on other ways the natural world and built world benefit from kinetic energy and potential energy. Some examples that students may want to discuss include:
Rollercoasters
Skateboarding down a hill or ramp
Trampolines, Pogo sticks, or other objects with springs.
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