Units

PHYS-TIKTOK Units video : scroll down

Physical quantities are specified by how it is measured or by how it is calculated from other measurements. For example, we distance and time are measured quantities , whereas average speed is a quantity that we calculate by dividing the distance traveled by time of travel.

Measurements of physical quantities are expressed in terms of units, which are standardized values. For example, the length of a race, which is a physical quantity, can be expressed in units of meters (for sprinters) or kilometers (for distance runners). Without standardized units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way.

Tik-Tok Problem 1:

Imagine that you are driving your car in Canada. As you're driving along, you notice that the speed limit signs have numbers like 120 (on the highway) and 50 (in the city). As you start to speed up, you realize that the signs are in km/hour. Unfortunately, your speedometer only reads in mi/hour. Figure out how fast you're allowed to go if the sign says 120 km/ h and 50 km/h

Unit Conversion Process

  1. Identify the unit you have. These are the units given to you in the problem

  2. Identify the unit you want. These are the Desired Units. In this class we will be using SI units for the most part

  3. Identify appropriate unit conversion factor(s). For this, either refer to the conversion sheets or refer the textbook

  4. Follow the unit conversion methods we discussed in the class, or any other way you are familiar with (e.g., chain rule). ...

  5. Evaluate the result.