Here is a quick project to demonstrate how sand helps to stop the train.
You will need:
2 Large Sheets of Paper
Glue or Glue Stick
1 Cup of Sand
2 Quarters
Scotch Tape
Take one piece paper and glue sand to the front of the entire page.
Once dry, tape this piece of paper to a table with the sand side facing up.
Tape the clean piece of paper next to the sand paper so they are side by side.
Place one quarter on each of the pieces of paper and using your pointer finger, try to slide the quarter across the papers at the same time. Did you notice how much slower the quarter moved across the sand paper? The friction from the sand slows down the quarter just like it slows the train wheel.
