Date: April 7, 2000

Grade Level(s): 2, 3

Subject(s):

• Science/Physics

Scientific Explanation:

What slows a parachute when it falls? A parachute is slowed by air resistance. Air is a collection of gas molecules that have to be pushed out of the way for any object to move through it. These molecules can exert force (pressure) on objects that try to push them out of the way. This is an example of Newton's 3rd Law (for every action there is an equal and opposite reaction). When you blow up a balloon, it is being held up by the molecules of air pushing on the plastic. When the parachute falls through the air, the molecules don't want to move so they push back, slowing the parachute. The parachute tries to moves through the air. As with any object, it encounters air resistance. That resistance is a result of air molecules resisting a change in motion and exerting an opposing force.

Goals:

Student Understandings:
1. A parachute falls slowly because there is air pushing back on it.
2. Any object that moves through the air is being slowed down by air resistance.

Objectives:

Students will:

1. predict how a parachute works using a sheet that includes a drawing or description.
2. provide a written example of applying air resistance to personal life.

Per student: 4 pieces of string 45 cm (18"), 4 adhesive dots ( or tape), 2 jumbo paper clips, 1 paper napkin

Procedure:

Focus Phase:

Hop flapping your arms and ask the students what you are trying to do. Once they have identified flying, have them brainstorm things or ways that people fly. Write their answers on the board. Identify parachutes as one answer. Use preconstructed parachute to demonstrate its operation to the class. Ask the students how the parachute works. Write the brainstorming ideas on the board. Reinforce ideas that relate to air holding the parachute up. Students will then individually draw a picture or write how they think a parachute works.

Challenge Phase:

Demonstrate to students how to build parachute. You will fasten the four pieces of string to the corners of the napkin using the adhesive dots. Tie the four strings together. Attach one paper clip as a passenger. Have students build parachutes. Show students one method of releasing a parachute. Students will then brainstorm other ways to release a parachute and predict how it will fall. They will then explore these ideas and test their predictions. Students can then also experiment with adding second paper clip. Ask them to predict what difference it will make on how the parachute falls.

Concept Introduction Phase:

Did the parachutes work? What were some of the ways the students discovered for how to launch the parachute? What were some that worked and some that didn't? Did adding the second paper clip make a difference on how the parachute fell? What was that difference and why do you think that was? Discuss with the students the idea of air resistance. It is the air that is pushing back on the parachute that is slowing it down. Define "resistance" by having a volunteer come before the class and raise an open palm. Push on the hand so that the student has to push back. Have a student go to the board and draw their idea of how the parachute works. Poll the class to see if they agree, why or why not. Talk about adding the second paper clip or any mass to the parachute. Why did the parachute fall faster? The mass of an object affects how strong (how much force) the air resistance can exert on an object.

Concept Application:

Move a variety of objects through the air: A piece of paper, pencil, and a ball. Ask the students if there is air resistance acting on those objects. Ask students what is happening when a newspaper blows down the street, and what is happening when you put your hand out the window of a moving car. When I drop this feather to the ground, why does it fall this way? Ask the students to pair up and come up with an example from their own lives of air resistance.