In today's activity, we will use water balloons to demonstrate how an orbit is the balance between gravity and the velocity of the spacecraft. An elliptical transfer orbit from Earth to Mars.Ĭopyright © 2004 Geoff Hill, ITL Program, College of Engineering, University of Colorado Do you know which gravitational force becomes the largest force once a spacecraft has gotten far enough away from the Earth? (Answer: The Sun's gravity takes over once the spacecraft has left the Earth's orbit.) Figure 1 illustrates the path of a spacecraft traveling in an elliptical transfer orbit from Earth to Mars it shows that the path from the Earth to Mars is not a straight line since the spacecraft is actually orbiting around the Sun.įigure 1. In reality, the spacecraft has not actually escaped the Earth's gravity, but it has gotten far enough away that it is not the largest gravitational force acting on our spacecraft any more. It takes a lot of energy to get enough velocity to "escape the Earth's gravity," however, once a spacecraft has done this, it can coast to Mars and only have to fire its rockets one more time to slow down as it approaches Mars. This is exactly what happens when we send a spacecraft to another planet, such as Mars. If the spacecraft continues to speed up, it will eventually be able to leave the Earth's orbit. What do you think would happen if a spacecraft orbiting the Earth kept speeding up? Would the spacecraft get closer or further from Earth? (Answer: Further) As the velocity of the spacecraft speeds up, it wants to keep going past and away from the Earth, which means gravity has a harder time keeping the spacecraft close and therefore the spacecraft enters an orbit that is further from the Earth. There is still gravity, but in an orbit, the tendency of an object to move toward the center is perfectly balanced by the spacecraft's tendency to continue in a straight line away from the planet. However, this does not mean gravity is not acting on the people in a spaceship. Do you think gravity is acting on an astronaut orbiting around the Earth? (Answer: Yes, Gravity is present but, you cannot see or feel it.) You might not think gravity is acting on astronauts because when we see videos from space, everything is floating around. All things that have mass are attracted to other things that have mass. Gravity is an attractive force between two objects. Orbiting Water Balloons Worksheet (pdf) Visit [ to print or download. Models can be used to represent systems and their interactions.Īlignment agreement: Thanks for your feedback! Science assumes that objects and events in natural systems occur in consistent patterns that are understandable through measurement and observation. This activity focuses on the following Three Dimensional Learning aspects of NGSS:ĭevelop and use a model to describe phenomena.Īlignment agreement: Thanks for your feedback!Įarth and its solar system are part of the Milky Way galaxy, which is one of many galaxies in the universe.Īlignment agreement: Thanks for your feedback! The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them.Īlignment agreement: Thanks for your feedback! The solar system appears to have formed from a disk of dust and gas, drawn together by gravity. Describe how gravity is still acting on an object that is in orbit.ĭevelop and use a model to describe the role of gravity in the motions within galaxies and the solar system.Ĭlick to view other curriculum aligned to this Performance Expectation.Articulate that to escape the Earth's gravity, engineers must design and build huge rockets.
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