Rolling like Galileo

After Galileo was put under house arrest, he returned to some of his earlier science work. In particular, he looked at the way things fall.

We looked at this video that told us about this:

Click to view video

There was lots of interesting vocabulary, quite difficult for Year 4, so we had a look at a Padlet wall of words to help understand some of it.

Galileo had found, for the first time, that there was a pattern of numbers in the way things fall: the odd numbers - 1,3,5,7...

The ball was speeding up all the time:

We are beginning to try to reproduce Galileo's experiment in the classroom.

What's this? Duplo? What's that got to do with it??

Well, the Duplo was holding our slope up.

We had to try different heights of Duplo to get a slow and even run of the ball.

This worked:

Time to time the run.

These are our times. On the left is the additional distance travelled, on the right the time from the start.

Here they are in a neater table:

Hmmm... This is not what Galileo predicted. He said that the numbers in the yellow column should be the same. But for us the ball was not speeding up as much as Galileo said it should be!

What could be wrong? Any ideas?