physics cw
Storyboard Text
- Hey Bob, why does the piece of wood and the beach ball float on water, but the stone and the coin don't?
- Well, Joe, that happens due to the density of these different objects.
- Bob, what is density?
- Density refers to the mass/volume of an object. For example, if an object weighed 10g and its volume was 5cm cb, its density would be 2g/cm cb.
- Bob, but what does that have to do with density?
- If the density of an object is more than that of water it will sink, but if it is lower, it will float. The density of the stone and coin is more than water so it sinks and that of the ball and wood is less, so it floats.
- Is this also why some objects feel heavier than others even though they occupy the same amount of space?
- Yes, Joe, very good. Now lets learn about the changes in density.
- Density can vary according to temperature and pressure. Applying pressure to an object decreases volume, which then increases density. Increasing the temperature of an object almost always decreases its density by increasing its volume.
- Wow! So does that mean that when water freezes and turns to ice its density increases becasue its volume decreases and when ice melts, the density decreases because the volume increases. So that means that volume and density are inversely related.
- very good observation Bob!
- Thanks for all your help Joe!
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