A500 lb steel beam is lifted up by a crane to a height of 100 ft and is held there. a) how much work is being done to hold the beam in place? b) how much work was done to lift the beam? c) how much work would it take if the steel beam were raised from 100 ft to 200ft?

A. How much work is being done to hold the beam in place?

Work is the product of Force and Displacement. Since there is no Displacement involved in just holding the beam in place, hence the work is zero.

B. How much work was done to lift the beam?

In this case, force is simply equal to weight or mass times gravity. Hence the work is:

Work = weight * displacement

Work = 500 lbf * 100 ft

Work = 50,000 lbf * ft

C. How much work would it take if the steel beam were raised from 100 ft to 200ft?

The displacement is still 100 ft since 200 – 100 = 100 ft, hence the work done is still similar in B which is:

Work = 50,000 lbf * ft

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