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This came out in ICAS Science this year.

Here is what happened:

By pouring hot water into a jar and trapping it, you created warm, moist air.  As the warm air inside the jar rose, it was then cooled by the ice on top of the jar.

When the water vapour cooled, it wanted to turn back into liquid, but it needed to condense onto a surface. The aerosol provided cloud condensation nuclei: a surface for the water vapour to condense into tiny cloud droplets.

The cloud swirled inside the jar due to the circulation of warm air rising and cold air sinking.

Refer: http://www.kidspot.com.au/things-to-do/activities/how-to-make-a-cloud-in-a-jar for more.

This video explains “mechanical advantage” in pulley system clearly.

The greater the “mechanical advantage” in a pulley system, the heavier the loads you can lift.

Also, in another type of pulley system consists of two pulley wheels each on a shaft, connected by a belt. This transmits rotary motion and force from the input, or driver shaft, to the output, or driven shaft.

If the pulley wheels are different sizes, the smaller one will spin faster than the larger one.

Let’s try this question:

Refer : http://www.bbc.co.uk/schools/gcsebitesize/design/systemscontrol/mechanismsrev7.shtml to learn more about velocity ratio, output speed and torque (turning force).

 

Try this question:

The earth rotates 360° in 24 hours, which means 15° an hour or 1° in 4 minutes.

After watching the video, let’s try this question.

The longitude of Rockhampton is approximately 150° E and the longitude of Dhaka is 90° E. What is the time in Dhaka when it is 6am in Rockhampton?

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