We had a Science presentation on Thursday and the groups presented their solutions together with their questions. As I was in Group 1, my group presented first...
Group 1's Question:
Estimate the amount of water in the MacRitchie Reservoir during the dry season if the depth is 2.5m.
Solution:
Use the cut and paste method. If we cut and paste, we estimated that it will be about 1.4cm by 2cm on the map and we calculated the answer, which came up to a really big answer. Here's the map below.
*There are also other solutions but this is one of the simplest we thought of.
Group 2's Question:
You are given a copper wire with a small diameter. The only instrument you have is a metre ruler. How can you measure the diameter of the wire as accurately as you can?
Their Solution:
Coil the wire around a pencil as close as possible. Measure the length of the pencil that was covered by the wire and count the amount of coils. Divide the length of the pencil by the number of coils.
*This was supposed to be a Secondary 3 question.
Group 3's Question:
How do submarines float and sink at will?
Solution:
At the side of the submarine, there are ballast tanks. To sink, air is let out and water is taken in. To float, air is filled and water is let out.
Food for thought:
When a submarine lands on a seabed, why is it unable to float back up?
Look at the picture above. When the submarine lands on the sea bed, the up thrust is gone and it cannot float back up again.
*This is JC Science...
Question 4.
In a production line, there are 1000 small screws. They must be packed into packs of 50. Counting would be too tedious. Is there another way that is faster?
Solution:
Use an electromagnet.
Adjust the resistance to attract only 50 screws
(Inappropriate-the electromagnet will either attract all or none of the screws)
Weighing scale. Count 50, weigh it. Note the weight of 50 screws. Next, estimate amount of screws, put on weighing scale and measure it to be about the previous weight.
Question 5:
Why is it that the spring balance has different readings on the Earth and Moon while the beam balance's reading, both on Earth and Moon, are the same?
Solution:
Spring Balance: measures Newton/weight. Weight depends on gravity and the gravity pull is different both on Earth and moon.
Beam balance: measures mass. Mass never changes.
That's all the presentations. Hope you learnt from it :)
Physics Presentation 22/1-29/1
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