The sun is located in the center of the system model because the sun: . * 1. is the least massive object in the system, and more massive objects orbit less massive objects.

2.is the most massive object in the system, and less massive objects orbit more massive objects

3. has the lowest temperature, and hotter objects orbit cooler objects.

4. has the highest temperature, and cooler objects orbit hotter objects.

2.is the most massive object in the system, and less massive objects orbit more massive objects

is considered as a single focus by the objects describing elliptical paths about the sun.

an enlarged virtual image

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day