What can you use for half track tracks?

They use guns at track meets because it ensures that the starters know when to start. If they didn't have the gun someone might not hear the referee say go.

1.7 grams

A linear air track is typically used in the study of motion in physics. Depending of the different tracks available, different experiments can be conducted. These range from proving the conservation...

the movements of the Sun, Moon, planets and stars.

you can use it by saying " I keep track of my dailey schedule everyday."