By what mechanism is a person injured when he or she falls from a significant height? select one: a. kinetic energy is converted to potential energy; the potential energy is then converted into the work of bringing the body to a stop. b. as the person falls, the amount of kinetic energy is converted into work; work is then converted to kinetic energy upon impact. c. potential energy is created as the person is falling; the potential energy is then converted into kinetic energy upon impact. d. potential energy is converted to kinetic energy; the kinetic energy is then converted into the work of bringing the body to a stop.

d. Potential energy is converted to kinetic energy; the kinetic energy is then converted into the work of bringing the body to a stop.

Explanation:

- At the beginning of the falls, when the person is still at a certain height h, the person has gravitational potential energy:

U = mgh

where m is the mass of the person, g the acceleration due to gravity, h the height above the ground.

- As the person falls down, h decreases, so the potential energy decreases; according to the law of conservation of energy, potential energy is converted into kinetic energy, since the speed of the person increases:

where v is the speed.

- Just before hitting the ground, all the potential energy has been converted into kinetic energy

- When the person hits the ground, he/she comes to a stop: so work is done by the ground on the person, because the ground applied a force required to stop the person, and the kinetic energy "lost" by the person is equal to the work done by the ground to bring the body to a stop.

an obstruction

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