Vehicle crumple zones are designed to absorb energy during an impact by deforming to reduce energy transfer to the occupants. How much kinetic energy, in Btu, must a crumple zone absorb to fully protect occupants in a 3000-lbm vehicle that suddenly decelerates from 10 mph to 0 mph?

change in KE = -12.95 Btu

Explanation:

given data

mass = 3000-lbm

velocity of vehicle initial vi = 10 mph = 14ft/s

velocity of vehicle final vf = 0 mph = 0 ft/s

solution

as here for crumple zone to protected zone it will absorb kinetic energy

so change in KE is related here initial and final velocity that is

change in KE = 0.5 × m × (vf² - vi² ) .................1

put here value and we get

change in KE = 0.5 × 3000 × (0² - 14.7² )

change in KE = -324135 × *  

change in KE = -12.95 Btu

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.