Why are radioactive isotopes useful in scientific research

According to social exchange theory, altruistic behaviors benefit the individual who performs them. t/f

What would be the result of an alpha particle coming into a magnetic field? a) the alpha particle will stop moving. b) the alpha particle will reverse its direction. c) the alpha particle will be deflected in a curve path. d) the alpha particle will continue to travel in a straight line.

Which pair of quantities includes one quantity that increases as the other decreases during simple harmonic motion?