Describing the Physical Universe Chapter 1 Section 2 Distance and Time

Measuring Distance What is a measurement? What is a measurement? A measurement is an exact value that tells you “how much”. A measurement is an exact value that tells you “how much”.

It is important that a measurement can communicate an amount in a way that other people can understand. It is important that a measurement can communicate an amount in a way that other people can understand.

45 Is this a measurement? Is this a measurement? It is not a measurement It is not a measurement Are we talking about apples or kiwis? Are we talking about apples or kiwis?

Miles Is this a measurement Is this a measurement This is not a measurement This is not a measurement Is there half a mile or 100 miles? Is there half a mile or 100 miles?

Every good measurement gives a quantity and a unit. Every good measurement gives a quantity and a unit. A unit of measurement is a standard amount of a quantity A unit of measurement is a standard amount of a quantity What separates a good unit from a bad unit? What separates a good unit from a bad unit?

Activity Activity Directions: Directions: Part 1: One at a time, everyone take your right hand and measure how many “hands” it takes to go around one lab bench. Part 1: One at a time, everyone take your right hand and measure how many “hands” it takes to go around one lab bench.

1 hand is from the tip of your longest finger to the bottom of your palm. 1 hand is from the tip of your longest finger to the bottom of your palm. Part 2: Using your own feet, measure how many feet it takes to get from the teachers desk to lab station 5. Part 2: Using your own feet, measure how many feet it takes to get from the teachers desk to lab station 5.

Put your results on the board.

Before measurement was standardized, the king where you were living would make measurements. Before measurement was standardized, the king where you were living would make measurements. A foot was how long the kings foot was. A foot was how long the kings foot was.

A cup was how much water the kings favorite cup could hold. A cup was how much water the kings favorite cup could hold. Now imagine living in medieval France, and the king of Spain ordered 500 cups of wine. How could this cause a problem? Now imagine living in medieval France, and the king of Spain ordered 500 cups of wine. How could this cause a problem?

Distance is the amount of space between two points. Distance is the amount of space between two points. The space between you and your friend, or the space between your house and the school are all distances The space between you and your friend, or the space between your house and the school are all distances

Distance is measured in unites of length. Distance is measured in unites of length. Some examples of length are inches, miles, centimeters or kilometers. Some examples of length are inches, miles, centimeters or kilometers.

Two Systems of Measurement These two systems are called the English System and the metric system. These two systems are called the English System and the metric system.

Only 3 countries in the world still use the English system Liberia, Myanmar, and USA

Another name for the metric system is the International System of Units Another name for the metric system is the International System of Units This can be abbreviated to SI This can be abbreviated to SI Almost all of science is measured using SI units. Almost all of science is measured using SI units.

This is because everything is measured in factors of 10. This is because everything is measured in factors of kilometer = 1,000 meters 1 kilometer = 1,000 meters 1 meter = 100 centimeters = 1000 millimeters 1 meter = 100 centimeters = 1000 millimeters

In this class, we will be using the metric system the most often but will occasionally use the English system. In this class, we will be using the metric system the most often but will occasionally use the English system.

Measuring Time The word time can have two meanings. The word time can have two meanings. It can be an exact moment or it can be a duration. It can be an exact moment or it can be a duration.

When you ask for the time, you want to know an exact moment. When you ask for the time, you want to know an exact moment. You then proceed to identify this moment by checking a clock. You then proceed to identify this moment by checking a clock.

You may also ask “how much time?” You may also ask “how much time?” For this you need a time interval. For this you need a time interval. A time interval is a quantity of time that has a beginning and end. A time interval is a quantity of time that has a beginning and end.

In this class, time will mostly be a time interval and measured in seconds. In this class, time will mostly be a time interval and measured in seconds. Time is usually represented by the variable t Time is usually represented by the variable t

The second is used in both the English and metric system. The second is used in both the English and metric system. Most often in physics, we will time an event in seconds, but sometimes we will have to consider a fraction of a second. Most often in physics, we will time an event in seconds, but sometimes we will have to consider a fraction of a second.

How much time is 3:27:41? How much time is 3:27:41? 3 Hours, 27 minutes, and 41 seconds 3 Hours, 27 minutes, and 41 seconds How many total seconds is this? How many total seconds is this? seconds seconds

Most commonly people give time in mixed units. Most commonly people give time in mixed units. –Hours, minutes and seconds In science, the time can only have one unit In science, the time can only have one unit –Usually seconds

Distance and Time Graphs If you want data on something, a table of numbers can usually be provided. If you want data on something, a table of numbers can usually be provided.

However, organizing these numbers into a graph will make them a lot easier to read. However, organizing these numbers into a graph will make them a lot easier to read. You need two variables to make a line graph. You need two variables to make a line graph.

The independent variable is placed on the x-axis (left to right) The independent variable is placed on the x-axis (left to right) We call it independent because we can choose to take the measurement. We call it independent because we can choose to take the measurement.

The dependent variable is placed on the y-axis (up and down) The dependent variable is placed on the y-axis (up and down) We call it dependent because this variable changes according to the independent variable. We call it dependent because this variable changes according to the independent variable.