Class exercise 4a

1. Does the shape of an object affect whether it floats or sinks? If a piece of plasticine is folded into a different shape, what changes aside from its shape?

A: Specifically, the shape of an object does not affect whether it floats or sinks, but the volume of the object that changes as its shape changes does so. For example, a lump of plasticine does not float. But if it is moulded into a cup, its volume increases, thus decreasing its density and allowing it to float.

However, if you submerge the plasticine cup, it will sink, therefore it is not the shape that allows it to float, but the increase in volume.

2. A piece of metal sinks in water, but a can (made of metal) floats in water. Why do you think this is so? Do you think the material determines whether the object sinks or floats?

A: The overall density of the can is less than that of water, as its volume is significantly greater than its mass due to the large volume of air inside it. However, the density of the piece of metal is much higher than the can’s as its volume is smaller than the can’s even though their masses are similar. Therefore, the material does not determine whether the object sinks or floats.

3. Why do some drink cans float, and some drink cans sink? Fill in the table below that will help you determine the factors that affect the density of an object.

 

Mass
(use the weighing balance)

Volume
(read off the can)

7-up

 

 

Pepsi

 

 

Coke

 

 

Coke Zero

 

 

 

Conclusion:

Screen Shot 2013-01-27 at 2.48.39 PM

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