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Skydive Into Forces

Summary

Grade Range
3rd
Group Size
2 students
Active Time
60 minutes
Total Time
60 minutes
Area of Science
Physics
Space Exploration
Key Concepts
Forces, speed
Credits
Sabine De Brabandere, PhD, Science Buddies
Four figurines attached to colorful tissue paper parachutes

Overview

Forces, which we might instinctively describe as pushes and pulls, are acting on us at all times, but we cannot always see them. This hands-on lesson offers a fun opportunity to explore "invisible" forces like gravity and air resistance. Students will build parachutes and investigate how they allow skydivers to safely land.

Learning Objectives

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices
Planning and Carrying out Investigations. Make observations and/or measurements to produce data to serve as the basis for evidence for an explanation of a phenomenon or test a design solution.

Analyzing and Interpreting Data. Compare and contrast data collected by different groups in order to discuss similarities and differences in their findings.
Disciplinary Core Ideas
PS2.A: Forces and Motion. Each force acts on one particular object and has both strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object's speed or direction of motion.
Crosscutting Concepts
Cause and Effect. Cause and effect relationships are routinely identified, tested, and used to explain change.

Materials

A ruler, scissors, string, tape, a hole punch and a small figurine

For each group of 2 students, you will need:

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Scientists refer to a push or pull as a force. Forces can change the movement of an object (its speed and/or direction), but they do not always do so. Imagine a grocery cart standing still. You can push on the handlebar to make it move (Figure 1, top left). If it is already moving, and you push it, you can make it move faster (Figure 1, top right).

Drawn figures push on a shopping cart to change the direction and speed it travels
Figure 1. Pushing on a shopping cart can change its motion. Red lines indicate the cart's speed, and blue arrows indicate a push. A push can make a cart move (top left), and an additional push can make it speed up (top right). Pushes in opposite directions can cancel each other out (bottom).

It gets a little more complicated when more than one force acts on an object. Imagine pushing the grocery cart again, but this time, another person is pushing equally hard on the opposite side of the cart. The two opposing forces would cancel each other out, and the cart's movement would not change (Figure 1, bottom). Most often, objects have many forces acting on them. We often do not realize this because some forces are canceled out by others and thus do not affect the motion of the object. For example, the shopping cart has mass, so gravity pulls it down—but the cart does not fall, because the ground pushes back with equal strength in the opposite direction.

In this lesson, students will study how forces can affect the speed of a falling object by looking at a skydiver. Without an open parachute, the skydiver is in free fall. Gravity pulls him or her down, and almost nothing is pushing back up to slow down or prevent the fall. The situation changes when the parachute opens. Suddenly, a lot of air particles need to move out of the way to let the open parachute pass. The air pushes the parachute—and the skydiver hanging from it—up, as shown in Figure 2. This push, or force, is called air resistance or drag. It has a direction opposite to the movement. In this case, this force acts in the opposite direction to gravity. As a result, the force of gravity is partially cancelled out and the skydiver does not gain speed as quickly. The skydiver falls at a slower pace and is able to safely land.

Photo of a skydiver where gravity pulls the skydiver downward and air resistance pushes the parachute upward
Figure 2. Forces acting on a skydiver coming down with a parachute.

As shown in Figure 2, scientists represent forces with directional arrows. The arrow points to where the force pulls or pushes. Gravity always pulls objects down, and air resistance always points against the motion of the object it acts upon.

Technical note: Scientists typically use arrows to represent forces and speed. To avoid confusion, in this lesson we will only use arrows to represent forces.

Prep Work (5 minutes)

Engage (5 minutes)

Explore (60 minutes)

Reflect (10 minutes)

Assess

Make Career Connections

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