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# Calculating Derived Quantities

## Measurements can be used in combination to describe physical objects in greater detail.

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Practice Calculating Derived Quantities
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Fast Ice

### Fast Ice

Credit: Elliot
Source: http://www.flickr.com/photos/pointnshoot/1426010816/

Ice hockey can be an exciting sport. The hockey puck can careen down the ice at speeds greater than 100 miles per hour! The players can also skate at very high speeds over the ice—at least they can if the ice is “fast.”

The Back Story

• That’s where hockey ice technicians come in. The ice tech is responsible for keeping the ice in tip-top shape so the players can perform at their best.
• Good ice starts with very pure water, so professional hockey rinks have machines to remove any contaminants from the water.
• Credit: Peter Psmithy
Source: https://www.flickr.com/photos/psmithy/2247038881

Ice technicians utilize vehicles that make sure the ice is ready to be played on [Figure2]

• Knowledge of the physical properties of water is also important, including its freezing point and density.
• Watch this video to learn more about the role of ice and ice techs in professional hockey: http://www.nbclearn.com/nhl/cuecard/56618

Can You Apply It?

1. Why is water a unique substance? What are some of its unusual physical properties?
2. Super-cold water circulates in pipes beneath the concrete floor of a hockey rink. How is this water kept very cold without freezing?
3. How would you calculate the volume of ice in a hockey rink?
4. What is mass?
5. What is density? Does it vary for a given substance? How can density be calculated?
6. If you know the density and volume of a substance, what formula could you use to calculate its mass?
7. The density of ice is $917 \ kg/m^3$. If the volume of ice in a hockey rink is $43.6 \ m^3$, what is the mass of the ice?
8. What is the difference between “fast” ice and “slow” ice in hockey? What determines whether ice is “fast” or “slow”?