Physics for Life Sciences

Lecture 2: Foundations of Measurements and Motion

Why are the foundations of units?

• Accurate experiments

• Safe medical dosages

• Clear communication about the world

How many units are in the SI System?

7

Dimension/SI Unit/Symbol for 3 units

Length Meter m

Time Second s

Mass Kilogram kg

Metric Prefixes

You can only compare two qualities if they have the same ____

Dimensions

You cannot compared ___ to ___, however you can compared ____ to ____, or ____ to ____

time; mass, seconds; years, kilograms; ounces

Dimensional Analysis (Factor-Label Method)

convert to the same unit

Unit conversion is the process ____

of expressing the same quality in a different unity of measurement. The actual amount of stuff (length, weight, time…) doesn’t change, just the way its labeled.

Position

the location of an object relative to a chosen reference point (the origin)

Distance

a scalar quantity. It represents the total length of the path traveled between two points, including units

Displacement

A vector quantity. It represents the change in an objects position, combining both a magnitude (distance) and direction. Mathematical difference between the final and initial position vectors

Scalar

physical quantity that has only magnitude (size). ex. distance, mass, time, speed

Vector

physical quantity that has both magnitude and direction. represented with arrows. ex, displacement, velocity, and force

Speed is ___

scalar

Speed

“how fast” something is moving. It is the rate of change of distance

Velocity is ____

vector

Velocity

Rate of change of displacement. How fast and in which direction an object is moving

Average speed

distance traveled/ elapsed time

Average velocity

Displacement/ elapsed time

instantaneous rate of change

how fast a quantity is changing at a single, specific instant time

Instantaneous speed

the magnitude of the instantaneous velocity

Instantaneous velocity

the average velocity in the limit as the change in time approaches zero