# Why is viciously shaking a jar of water work in the thermodynamic sense?

According to thermodynamics, internal energy can only be increased either by doing work on the system or heating the system. Work done on the system is defined by $$W=-P_\text{external}\times\Delta V$$

So when a jar of water is viciously shaken, the temperature of the water inside is increased. How is work done correlates over here?

• This can be called "work" but it is different from pressure-volume work which requires change in volume. – samjoe Nov 11 '17 at 13:43
• There are many ways to do "work", i.e. transfer energy. If you put a resistor in a sealed, and allow electricity through, it will also get hot. In 1798, Benjamin Thomson showed that kinetic energy can be changed to thermal energy... but the details are boring. – DrMoishe Pippik Nov 12 '17 at 3:16