In thermodynamic process, pressure of a fixed mass of a gas is changes in such a manner that the gas molecules gives out 20 J of heat and 10 J of work is done in the gas. If the initial internal energy of the gas was 40 J, then the final internal energy will be

Options

A. 30 J
B. 20J
C. 60 J
D. 40 J

Answer

A

Explanation

`Delta Q= -20 J, Delta W= -10 J`
`Delta Q=(U_f-U_i)+Delta W`
`implies -20=(U_f-40)-10 implies U_f = -10+40 = 30J`