If `20kJ` work is done by the water fall per unit volume of water and `30kJ` heat was lost per unit volume, the energy change per unit volume of water is:

Options

A. `-5 kJ`
B. `-50 kJ`
C. `10 k J`
D. `+50 k J`

Answer

C

Explanation

`q=DeltaU+(-w)`
`-30=DeltaU-20`
`:' w=+20 kJ`
`:. DeltaU=-10 k J`