Goal: Understand the concepts related to gravitational forces and flight through critical-thinking and graphing skills. Use math skills to calculate speed and forces needed for movement.

Time Required: 40 minutes

Materials Required: Chart/graphing paper, pencil/pen, straight-edge/ruler, Gravity On Earth Student Reproducible 1 (PDF)

Directions:
1. Write “gravity” on the board. Have students brainstorm meanings and other terms they associate with this word. Ask students how they think objects from the earth counteract gravity to get off the ground.

2. Review Sir Isaac Newton’s theory of gravity with students and explain that gravity draws (attracts) objects to the earth. Review the following facts:

• The basic law of gravity states that gravity is the attraction between any two objects that have mass. The mass of an object is the amount of physical matter that it contains.
• All objects attract each other due to gravitational force. For example, we are attracted toward the earth and the earth is attracted to us. However, on earth it is difficult to observe this attraction with the naked eye.
• Since the mass of the earth is so great, the objects on its surface weigh virtually nothing compared to it.
• The earth’s gravitational force overpowers objects’ attraction to any other objects.

3. Distribute Gravity On Earth Student Reproducible 1 (PDF). Discuss the following example with students.  If an object, such as a helicopter, had to escape the earth’s gravitational pull, it would need to generate (and sustain) an amount of lift greater than its own weight in order to take off from the ground. The more lift that is generated, the higher the helicopter will rise. The heavier the object, the greater lift force is needed.

4. In order to further illustrate the relationship between gravity and flight, discuss the following example. Explain to students that in order for a helicopter to move horizontally, it needs to generate thrust (the forward force produced by an engine) greater than the drag force (the resistance caused by the shape of an object and its movement through the air). A helicopter generates thrust by changing the propellers’ direction. For example, if the pilot directs the main rotor blades forward, the helicopter will move forward. The speed or the velocity of the helicopter depends on the amount of thrust generated.

5. As a class or in small groups, complete the worksheet.

Wrap-Up:
Have students draw a map of their route home from school, either on foot or driving in a vehicle, estimating the time it takes between left and right turns and the distance between the turns. Have the students calculate the average velocity between turns and then calculate the overall velocity of the trip from school to home.

Answer Key:
1) More than 16,000 kg of lift; 2) 160,000 kg of thrust; 3) A) 37.5 km/hr., B) 50 km/hr., C) 80 km/hr., D) 37.5 km/hr., E) 50 km/hr.; 4) 350 km.; 5) 7.25 hrs.; 6) 46.67 km/hr.