A physic student conducted an experiment in which a spring is clamped into the ceiling and a mass is hanged at the bottom of the spring, The mass is increased and the length new length of the spring is
recorded
Mass
Distance (cm)
50
54
80
56
110 140
59 61
a) Identify the independent and dependent variables in the expenment

The answer; They used a stable isotope and tracked it with a Becquerel counter

An example of stable  isotopes is 14-C and 2-H. These types of isotopes have an atomic decay that leaves less radioactive material behind, hence safe for laboratory use and used without harming the normal processes of life being investigated. Bq is the unit preferred for this type of radioactivity.