In the dangerous sport of bungee jumping, a daring students jumps from a hot air balloon with a specially designed elastic cord attached to his waist. the unstretched length of the cord is 25.0 m, the student weight 700 n, and the hot air balloon is 36.0 m above the surface of a river below. base on a principle of conversation of energy, calculate the required force constant of the cord if the students is to stop safely 4.0 m above the river.

910 N/m

Explanation:

The student starts 36.0 meters above the river and ends 4.0 meters above the river, so he falls a distance of 32.0 meters.  The cord has an unstretched length of 25.0 meters, so it gets stretched 7.0 meters.

Conservation of energy:

Gravitational PE = Elastic PE + gravitational PE

mgh = ½ kx² + mgh

(700 N) (36.0 m) = ½ k (7.0 m)² + (700 N) (4.0 m)

k = 914 N/m

Rounded to two significant figures, the stiffness of the bungee cord is 910 N/m.

truck y has a greater velocity than truck x.