Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine

Why do we use the metric system in science?

Remember A system based on multiples of 10 is much more intuitive for humans We are born with 10 fingers and toes The math system that we use is based on 10,

Metric System Any system of measurement needs three fundamental units –Length - meter –Mass - kilogram –Time - second

1 kilometer = 1,000 meters 1 meter = 100 centimeters 1 centimeter = 10 millimeters 1 kilogram = 1,000 grams

Things you need to know because we will use the metric system one kilometer is 5/8 of a mile one meter is 3.28 feet one centimeter is 0.39 inches 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth We will use the metric system in this class Does anybody remember the Mars Climate Orbiter?

Mars Climate Orbiter Software calculated forces for the thrusters in English units (pounds). People controlling the spacecraft thought the calculated forces were in Newtons (metric). (One English pound of force equals 4.45 Newtons.) Changes made to the spacecraft's trajectory were actually 4.45 times greater than what the JPL navigation team believed. The spacecraft missed its intended km altitude above Mars during orbit insertion, instead entering the Martian atmosphere at about 57 km. The spacecraft was destroyed

Exercise #2 1 kilometer = 1,000 meters 1 meter = 100 centimeters 1 centimeter = 10 millimeters 1 kilogram = 1,000 grams one kilometer is 5/8 of a mile one meter is 3.28 feet 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth

Meter How is the meter defined?

Meter Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole International Prototype Meter was defined as the distance between two lines on a standard bar composed of an alloy of ninety percent platinum and ten percent iridium, measured at the melting point of ice.

Meter Now defined as equal to the distance travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second.

Gram and Kilogram How are the gram and kilogram defined?

Gram and Kilogram How are the gram and kilogram defined?

Gram and Kilogram A gram was first decreed to be equal to “the absolute weight of a volume of water equal to the cube of the hundredth part of the meter, at the temperature of melting ice.” Now, the International Prototype Kilogram is used as the standard. It is made of a platinum alloy known as “Pt ‑ 10Ir”, which is 90% platinum and 10% iridium

International Prototype Kilogram Photo of Danish national kilogram prototype

Second The solar day was divided into 24 hours, each of which contained 60 minutes of 60 seconds each So the second was 1 ⁄ of the mean solar day. Now defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.

Any Questions?