The Great Gravity Escape

Students use water balloons and a length of string to understand how the force of gravity between two objects and the velocity of a spacecraft can balance to form an orbit. They see that when the velocity becomes too great for gravity to hold the spacecraft in orbit, the object escapes the orbit and travels further away from the planet. In this lesson, students will learn about gravity as related to the planets.

Standards & Objectives

Academic standards
GLE 0507.12.1
Recognize that the earth attracts objects without directly touching them.
GLE 0507.T/E.4
Recognize the connection between scientific advances, new knowledge, and the availability of new tools and technologies.
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Learning objectives: 

After this activity, students should be able to:

  • Understand that an orbit is the balancing of object's velocity with the gravitational force.
  • Realize that as the velocity of an orbiting object increases, gravity has a harder time keeping the object close.
  • Understand that engineers must design and build huge rockets to escape the Earth's gravity.
  • Understand that gravity is still acting on an object that is in orbit even though it is a weightless environment.

Lesson Variations

Blooms taxonomy level: 
Extension suggestions: 
  • Have students weigh different balloons and see if they can find a relationship between the mass of the balloon and the escape velocity. The students should see that a heavier balloon releases at a lower velocity. (Note: To see this result, the mass of the larger balloon must be significantly heavier — at least 50%.)