Question

1. Ferdinand is going up sky diving.  An airplane flies him up to 10 000 ft.  He jumps out.  He free falls and at 5000 feet opens his chute and eventually safely lands on the ground.  

a) What originally did work on Ferdinand? _____________

b) What originally was the work done against? _______________  

c) At what moment did he have the maximum potential energy? ___________________  

d)At what moment did he have maximum kinetic energy? ___________________  

e) When he landed on the ground, he lost some energy compared to when he stared his journey.  Where did the lost energy go and how was it lost? ________________________________________________________________________

Answer 1

(a) The airplane did work on Ferdinand, because, it changed the energy of him by carrying him upward.

(b) The work done by Ferdinand ( and the airplane too ) was against the earth's gravity, because, the vertical height increment was against the earth's gravitational attraction force, which acts downwards.

(c) Ferdinand had the maximum potential energy at 10,000 ft, because, his height was maximum there, and potential energy is directly proportional to the height of an object.

(d) Ferdinand had the maximum kinetic energy at 5,000 ft, because, upto that height his velocity was increasing during downfall, at that point his velocity was maximum, and, after that point his velocity was gradually decreased by the chute.

(e) The lost energy was utilized by the chute to decrease the velocity, and hence kinetic energy of Ferdinand, and the work was done by the air resistance on the chute to decrease the velocity of downfall.