Gravity
The moon doesn't smash into the earth because the gravity from the earth keeps the moon in orbit around it.
In my opinion, calling exercise "work" wouldn't be a good way of describing it, I don't think people would exercise if its called work
C. Electrical current increases as resistance decreases
Answer:
2.31J
Explanation:
the energy for a spring system is given by:

where
is the spring constant:
and
is the distance stretched from the equilibrium position.
In the first case 
so the energy to stretch the spring 1.81cm is:

and for the second case, the energy to stretch the spring 5.79cm:


so to answer a) we must find the difference between these energies:
