What is the closed physical system? A. Non of the answers are true

B. A system where matter and energy can leave but not enter the system

C. a system where matter and energy can leave but not enter the system

D. A system where matter and energy can not enter or leave the system

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

First answer marked as brainiest which is the correct equation describing the first law of thermodynamics? a) when the internal energy of a system changes, it equals the amount of heat added plus the work done. b) when work is done by the piston, it is equal to the heat added plus the change in internal energy of the system. c) when heat is added to the system, it is equal to the amount of work done by the piston plus the change in internal energy of the system.

Aprotein molecule in an electrophoresis gel has a negative charge.the exact charge depends on the ph of the solution, but 30 excesselectrons is typical. what is the magnitude of the electric forceon a protein with this charge in a 1500 n/c electric field?