Jim and Carla are scuba diving. Jim started out 8 feet below the surface. He descended 20 feet, rose 7 feet, and descended 12 more feet. Then he rested. Carla started out at the surface. She descended 15 feet, rose 7 feet, and descended another 20 feet. Then she rested. Which person rested at a greater depth?

Jim.

Step-by-step explanation:

Descending results in a greater depth so we add the measurements when they descend and rising results in a lower depth so we minus the measurements when they rise. The surface area has no depth yet, so it is 0 feet depth.

Jim = 8 + 20 - 7 + 12

     = 33

Carla = 0 + 15 -7 + 20

         = 28

Since 33 feet is deeper than 28 feet, Jim rested at a greater depth.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.