What has the greatest amount of potential energy? A. a 5 kg rock raised 5 m off the floor
B. a 2 g penny in an airplane at 1000 m above the earth
C. a 2 kg boulder at the top of a 10 m hill
D. a 0.5 kg book at the top of a 100 m hill

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.

Explain what will happen if decomposers were apsent from a forest ecoysystem.