Space Stations - Follow the Bouncing Ball!
In Follow the Bouncing Ball, children ages 8–13 predict whether a ball on Earth or a ball on the Moon bounces higher when dropped (or thrown at the floor) and why. They simulate the experiment by dropping, high and regular bounce balls from their shoulder height.
What's the Point?
- In microgravity, a little energy allows you to go a long way!
- Gravity causes us to return to the ground when we jump on Earth or the Moon or Mars. The smaller the force of gravity on us, the less we have to work to jump, and the higher we go!
The following materials are for one Follow the Bouncing Ball activity set
Three sets are recommended for a station
- 1 high-bounce ball (Not all high-bounce balls actually are. Test them to make sure!)
- 1 jacks ball or other low-bounce ball
- 1 permanent marker
- Children's Guide for Follow the Bouncing Ball
You may substitute other pairs of balls for high-bounce and jacks balls, as long as they bounce at noticeably different heights.
For the facilitator:
- With a permanent marker, label all the low-bounce balls "Earth" and all the high-bounce balls "Moon."
- Place the balls at the station with a copy of the Children's Guide for Follow the Bouncing Ball.
Described in the Children's Guide
The children should observe that the "Moon" ball bounced much higher than the "Earth" ball. The Moon has a smaller mass than Earth, and therefore a smaller gravitational "pull." Balls will bounce higher, for longer, and slower than those dropped on Earth. Without any pull of gravity — such as in space — an object would be able to bounce very high. In fact, it would just keep on going and going and going.
Astronauts can jump high on Earth, higher on the Moon, and really, really high in space. They have to do more work and use more energy on Earth to jump, and less on the Moon, and essentially none at all in space. But because it takes so little work to jump and move in space, astronaut's muscles weaken. In space and on Earth, humans have to exercise to keep their muscles strong and healthy.
A Little Background for the Facilitator
Astronauts have tried this experiment in space! When they drop a bouncy ball it doesn't go anywhere — it just hangs in space. But when they throw the ball at the floor, it bounces back at them and keeps going until it hits the wall of the Space Station! Then it bounces back and forth and back and forth. Very, very gradually it loses a little bit of energy each time it hits a wall. If the wall of the Space Station were not there for the ball to bounce off, the ball would keep going in space!
On Earth, that same bouncy ball, when dropped, would fall to the ground because gravity pulls it toward the center of the Earth. The same thing would happen on the Moon. On Earth, the ball would bounce back up to almost the height from which it was dropped, and then it would continue to bounce, each time a little less high until it stops. The ball loses a bit of energy with each bounce. On the Moon, with gravity 1/6th that of Earth, the ball would bounce higher, but more slowly, for longer.
So should future Olympics be hosted at the International Space Station or on the Moon? On the Moon, astronauts can jump higher than on Earth because of the lower gravity. On the Space Station, with little effort or use of energy, astronauts could jump infinitely high — unless they are stopped by a tether or the walls of the station!
February 9, 2010