Air Resistance: Coffee Filters● Drag Force● Terminal velocity● Derivation for lab ● Sample Data ● Pre-lab ● Results: correlation coefficient ● Please read 6.4 prior to completing pre-lab

Why shape a car like this?

What is air drag proportional to?

Drag force is the resistance force caused by the motion on an object through a medium (water, air, oil)

The power of velocity depends on the fluid

(For lab: What is the best relationship?)

C= Drag coefficient (dependent on object)ρ= Density of the fluidA= Area of object facing fluidv= Instantaneous velocity of the object

Drag Force

As a skydiver falls faster and faster through the air, what happens to the drag force?

increases

What happens to the net force?

decreases

Terminal VelocityWhen air resistance balances the weight, the objects stops accelerating and falls with constant velocity called terminal velocity

ACTIVITY (m=100 kg)10 m/s2

6 m/s2

0 m/s2

-2 m/s2

-20 m/s2

0 m/s2

The heavier object requires greater air resistance to balance its weight and therefore more speed so the heavier object accelerates

longer and has a greater speed and greater terminal velocity.

Terminal Velocity: Mass

Terminal Velocity How do we find terminal velocity?

Lab: Determining air resistance with coffee filtersThe goal is to determine what power of terminal velocity is a proportional to the drag force.

How will you calculate drag force?

Which relationship is better? Is this always the case?

Taylor’s graphs please don’t copy Taylor’s graphs please don’t copy

R-squared

● Statistical measure of fit that indicates how much variation of a dependent variable is explained by the independent variable in a regression model

● R-squared values close to 1 indicate a good fit

Drag Coefficient

Find drag coefficient of an 1.64-g coffee filter in free fall.

Using slope of fit find drag coefficient.