Galileo and the Pendulum

When Galileo was in church in Pisa he started watching the light hanging from the ceiling. It was swinging.

He was interested in how it was moving. Sometimes the wind would blow and it would swing more, then gradually it would slow down.

So he began experimenting with pendulums. He tried changing the size of the swing, the weight at the end of the string and the length of the string, and each time measured how long the swing took.

We used a timer to time ten swings of a pendulum.

We tried it with a big swing and with a little swing and found that the time the swings took was almost the same.

Galileo found the same thing and used the sameness of the pendulum swing to design a clock that would keep steady time: a pendulum clock. This was the beginning of pendulum clocks:

How the pendulum gives the tick tock of the clock

Galileo's design

The design built

Here it is, made out of cardboard by J. E. Johnson:

Pendulum clocks meant that people could measure time accurately at last. Before they could measure to the hour, now they could measure to the minute, the second even. Galileo's discovery changed the world.

Slope and Distance

After our friction experiments, both classes have been looking at other aspects of forces. In 4G we've been looking the angle of our slope.

We used a protractor to work out what angles were possible on the slope.

We wanted to see how the angle of the slope affects the distance a car goes after it runs down the slope. So, we tried it at lots of different angles, keeping every other variable the same.

We recorded what we found:

In some cases, the bigger the angle was, the further the car went:

Graphed with Desmos

In other cases, as the angle got bigger the distance got longer, but then, after a certain point, it got shorter again:

 Here's a chart that joins together all our results with an average result:

We talked about why there was that strange dip at the end. We had some good answers.

But what do you think?

Friction

Children in 4G have been testing different materials to see which one slows the car down the most (has the most friction).

When we did it in small groups we didn't all get the same result, so today we tried it again, the whole class working together.

These are the results we got:

So, we found out that there's the most friction with the bumpy carpet. And the least friction with the rubber.

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In 4B we did the same question but in a different way.

Here are our results:










Good news!  We also found that the bumpy carpet (purple carpet) had the most friction.  The smooth rubber had the least amount of friction.

However, we were surprised at our results for the two types of sand paper.  We had talked about the textures and really thought the rough sand paper (yellow sand paper) would have the most friction.  Many of us were wrong!

Friction - settling a question

Talking about friction, we rubbed our hands across the desk and the carpet. "Which is easier?" asked Mr Gregg. We couldn't agree: some thought the desk, some thought the carpet.

So... a scientific experiment. Measure the force it takes to move a stone in a bag on the two surfaces. Which would take more force?

The carpet took more force: 10 Newtons, compared to just 5 on the desk. There must be more friction on the carpet.

But Tibo said, "It's not fair. The bag makes it easier on the desk."

Half the class agreed. So we untied the bag, and tried the stone directly on the two surfaces:

This time it took 10 Newtons on the carpet, and only 2 Newtons on the desk. There's definitely more friction on the carpet!

Now the only question is, why didn't we agree that in the beginning?

Weighing Pebbles

Year 4 have been using forcemeters to measure the weight of pebbles and rocks. 

First we looked closely at the forcemeters.  We noticed some forcemeters had different scales:













We then worked cooperatively in small groups interpreting the scale and helping each other check the results.

After we had finished recording our measurements, we compared  our results with the rest of the class to see how accurate we were.  We were in fact very pleased, as we had lots of answers the same!