Considering only the initial and final situations, identify which mechanical energies have changed. In addition, determine whether you will need to consider any work done by external forces or changes in thermal energy.

Check all that apply.
A) Kinetic energy has changed.
B) Gravitational potential energy has changed.
C) Spring potential energy has changed.
D) Work by external forces on the system must be considered.
E) Thermal energy of the system has changed.

You are the coordinator for a program that is going to take place at night in a rectangular amphitheater in the mountains. you will have no access to any electricity, but you must be able to illuminate the entire grounds. you know the intensity of the light from a lantern varies inversely as the square of the distance from the lantern. suppose the intensity is 90 when the distance is 5 m. a. write an equation to model the situation. b. solve for the constant of variation. c. write the equation to model the situation using the constant () of variation. d. you have been given lanterns with 40 light intensity. use your equation to solve for the distance from the lantern. e. you need to illuminate 225 km. how many meters do you need to light? f. how many lanterns will you need?