An object gains 10 joules of potential energy as it is lifted vertically 2.0 m. If a second object with one-half the mass is lifted vertically 2.0m, the potential energy gained by the second object will be a. 10j
b. 20j
c. 5.0j
d. 2.5j

its first and third is your answer i did the qustion the fourth isnt right

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.