A 1-m3 tank containing air at 25 o C and 500 kPa is connected through a valve to a second tank containing 5 kg of air at 35 o C and 200 kPa. When we open the valve we let the system to reach thermal equilibrium with the surroundings, which is at 20 o C.

What happens in a global convection cell

The least penetrating form of radiation is

Suppose that 27 j of work is needed to stretch a spring from its natural length of 6 m to a length of 9 m. (a) how much work is needed to stretch the spring from 12 m to 14 m? j (b) how far beyond its natural length will a force of 78 n keep the spring stretched?