A child pushes a toy car down a hill. After 5 seconds, the car has a kinetic energy of 115 J and a gravitational potential energy of 30 J. What is the car’s mechanical energy at that time?

A) 3.9 J
B) 85 J
C) 115 J
D) 145 J

Radioisotopes often emit alpha particles, beta particles, or gamma rays. the distance they travel through matter increases in order from alpha to gamma. each radioisotope has a characteristic half-life, which is the time needed for half of a sample of radioisotope to undergo nuclear decay. which quality is desirable for a radioisotope that is used for medical imaging of a specific organ? check all that apply. half-life of several years half-life of several days half-life of several seconds emission of gamma rays emission of alpha particles ability to be attached to a compound used by the body ability to pass through the body without being absorbed