Fermi Problems

Dr WetzelIOT/FOT

Progress Report

• Why are you at Poly?• What do you hope accomplish in your next four

years?• What can make this course better?• What can you do to make the course better?• What can Dr Wetzel do to make the course

better?• What can you do to be better prepared for

class?

Objective

• Fermi Problems– Train us to identify the important parameters in a

problem– Make us think about units and how to convert

between different units– Allow us to calculate a rough estimate without

performing detailed experiments or complicated equations

Example

• How many ping pong balls fit in this room?– What assumptions do we make?– What parameters do we need to solve the

problem?

Ping Pong Balls

• We need to calculate volume of the room Vroom

• We need to calculate volume of ping pong ball Vball

• The number of ping pong balls that can fit in this room is Vroom/ Vball

Classwork

• How much land is needed to grow all of the Christmas trees in the United States?– What are the important parameters• How many people live in the United States• What percent of households celebrate Christmas• How much land does it take to grow a tree• Etc…

– What are reasonable estimates for each parameter

– What is the final answer

Classwork

• Reasonable assumptions– 300,000,000 people live in the United States– 4 people per household– 70% of households celebrate Christmas– 50% of households buy a tree– It takes about 10ft x 10ft to grow a tree– It takes about 10 years to grow a tree

Classwork/Homework

• Estimate how much soda the American population drinks in a year

• If a can of Coca-Cola is 150 calories and there are 3,500 calories in a pound of body mass, what is the average weight gain of an American in a calendar year due to drinking soda?