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.
Students examine the force of gravityCopyright Wikimedia Commons http://upload.wikimedia.org/wikipedia/commons/c/c2/Solar_sys.jpg
Engineers and scientists make amazingly precise calculations so that a spacecraft's journey is timed exactly to reach the location where a planet will be at that time. Since Earth and Mars are always orbiting in their own paths, space travel from Earth to Mars might be compared to shooting a basketball into a moving hoop while standing on a moving platform. This requires that engineers think logically and use their math skills to forecast exactly where a planet will be located many months in the future.
After this activity, students should be able to:
- Explain that an orbit is the balancing of the object's velocity with the gravitational force.
- Relate the increase in velocity of an orbiting object with the object getting farther away.
- Articulate that to escape the Earth's gravity, engineers must design and build huge rockets.
- Describe how gravity is still acting on an object that is in orbit.