What element has 81 protons in the nuclei of its atoms?
a. platinum
b. uranium
c. lead
d. thallium

What energy conversion occurs when a sling shot is used to shoot a rock across the room? (2 points) question 2 options: 1) stored mechanical energy is converted to mechanical energy. 2) stored mechanical energy is converted to radiant energy. 3) gravitational energy is converted to radiant energy. 4) gravitational energy is converted to mechanical energy.