The foam rocket flies ballistically. It receives its entire thrust (forward motion) from the force produced by the elastic rubber band. The rubber band is stretched when you set up the rocket to launch. When the rocket is released, the rubber band quickly returns to its original length, launching the foam rocket forward in the process. Technically, the foam rocket is a rocket in appearance only. The thrust of an actual rocket typically continues for several seconds or minutes, causing a continuous acceleration, until the propellants fueling the rockets launch are used up. The foam rocket gets a quick pull and then coasts until it is brought down by air friction and gravity.

Furthermore, the mass of the foam rocket doesn't change in flight. Real rockets consume their propellants through their engines. This makes the rocket lighter and means that the rocket will then need less propellant to continue its journey. Nevertheless, the flight of a foam rocket is similar to that of real rockets. Its motion and course is affected by gravity and by drag (friction in moving through the atmosphere).

NASA sends spacecraft equipped with robotic arms to explore places where humans cannot yet visit...like Mars...and distant asteroids. These arms have to be strong and adaptable. It is a highly used part of any robot since the arm is where a lot of work gets done. For rovers on Mars, it's where many of the tools are placed since it's what comes into contact with the Mars' surface and is used to extract samples.

Robotic arms and human arms have similarities. Both use flexible parts (string vs. muscle) to move their rigid parts (cardboard vs. bone). The pull of the strings or muscles is directed by a guide (straws vs. tendons). The position of the guides can affect the arm's efficiency.

The object of this challenge activity is to design and build a robotic arm that can lift a plastic cup or other small object off of a flat surface.