1.2.1 Physical Quantities and Units of Measurement

Question 1

Physical Quantities and Units of Measurement

Answer 1

• In order to make a quantitative statement about any physical system you’ll need to make measurements, which in turn require a unit system or standards.
• Throughout the course you’ll learn about the unit system used in the physical sciences: the metric system or Système International.

Question 2

note 1

Answer 2

• Physics is about describing and predicting the behavior of things. The first step is to make quantitative statements about the world around us. Units can be chosen arbitrarily, but they are of little use if there is no universal consensus about them.When you are making measurements you want to compare with a standard. In general this is not possible, instead you will use a calibrated device. You can always transform your measurements to different units. For example, one kilogram(kg) is equivalent to 2.2 pounds (lb).

Question 3

note 2

Answer 3

• In physics we use the metric system, also known as the mks system, which adopts the meter (m) as the unit of distance,kilogram (kg) as the unit of mass, and second (s) as the unit of time. meter: length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second kilogram:the standard of this unit is a block of platinum preserved at the International Bureau of Weights and Measures in France second: duration of 9,192,631,770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom

Question 4

mks system

Answer 4

• unit of distance: meter (m)
• unit of mass: kilogram (kg)
• unit of time: second (s)

Question 5

cgs system

Answer 5

• unit of distance: centimeter (cm)
• unit of mass: gram (g)
• unit of time: second (s)

Question 6

Which of the following uses a derived SI unit measurement?

Answer 6

speed

Question 7

In physics (and in all science) standard units are used to ensure measurement uniformity. Which of the following fictitious units of measurement could not be considered a standard unit?

Answer 7

The pinkie: a distance unit equal to the exact length of the right pinkie finger on the current U.S. president.

Question 8

What are SI units?

Answer 8

Systeme Internacionale units of measurement

Question 9

Which of the following best explains why physicists need to use standard units when making measurements?

Answer 9

To make accurate quantitative observations about the physical properties and behavior of things.

Question 10

Which of the following statements about SI distance units is not correct?

Answer 10

Converting a meter to feet is an example of a conversion involving two different SI units for distance.

Question 11

Which of the following best defines a second as an SI unit of time?

Answer 11

the amount of time that a cesium atom needs to vibrate a specific number of times

Question 12

Which of the following does not explain the use of SI units in physics?

Answer 12

SI units are more difficult to manipulate than old English system units (such as the foot and the pound).

Question 13

The SI unit for mass is the kilogram. Which of the following statements related to mass is not correct?

Answer 13

The definition of a kilogram is based on the mass of a certain number of carbon atoms.

Question 14

Which of the following statements about SI units is not correct?

Answer 14

The cgs system is not considered a standard SI system