## anonymous 4 years ago why the internal energy is 0 in case of isolated system? I mean, how the dq and dw are both 0

1. anonymous

In an isolated system, dQ and dW are zero because there is no change in heat or work.

2. anonymous

how no change in work...i can understand that dq is 0..but please explain that hoe dw is 0

3. anonymous

given$W=\delta E_k=1/2*m*(v_2^2-v_1^2)$as there is no external force (heat, pressure, etc.) the average velocity of the atoms will not change (some might speed up or slow down as they hit each other, but the average stays the same).

4. anonymous

this is the best explanation i have got...thanks for mending my concept

5. anonymous

It's what I do ;)

6. anonymous

What you mean it say is the the change in energy is zero for an isolated system, and that heat and work must both appear at the boundary of a system, because by definition they measure flows of energy across the boundary.