Can someone Plzzz help meee.

Determine the age of a fossil if it had only one eighth of its original carbon-14 content remaining?

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

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •