Propose an experiment that could be used to demonstrate that friction is a contact force? Pls help

In the first law of thermodynamics, triangle e=q-w, what does q stand for

What’s #16 asking me and how do i solve it?

Daughter element the new element produced along with a decay particle in a nuclear transmutation 2. half-life the substance that decays in a nuclear transmutation 3. parent element the change of one chemical element into another by nuclear decay or radioactive bombardment 4. transmutation the time required for the decay of one-half of the atoms in a sample of radioactive material