Question

This question is about work and pressure A frictionless piston cylinder contains a gas at a pressure of 200 kPa. The cross-sectional area of the piston is 0.04 m². Heat transfers to the gas, and as a result, the piston and load are raised through a distance (*) of 0.4 m. Assume the atmospheric air pressure to be 100 kPa. (Hint: this process is isobaric) 0 Is this an open system or a closed system and why? [2 marks] (I) Draw a sketch showing the process occurred from the initial to the final states, include a p-V diagram. [3 marks] (ii) Calculate the total work done by the gas. [3 marks] If the system is redefined to include the gas and the piston, determine (iv) The total work done by the system (gas and piston). (v) The total work done by the surrounding. [4 marks] [3 marks] [2 marks] (vi) in your own words, explain how work and heat are related in terms of energy in thermodynamic.

Answer 1

Sole closed system i The given problem is an example of З, і, луч л то transfer between system and surrounding but energy transfer is taking place in the form of heat and work. ين) A=0.04 m2 P V Piston 0.4m . Cylinder (iii) Treating the gas only as the system Assumption:- Work done by the system work done on the system Heat transfer to the system = tve Heat transfer from the system - tue ↑ ? 'T -ve

We know, Wark Done = PAV (200 K 103 ) X 1x (oroukous W 3200 J 3.2 ks Work Done by the gas 3.2ks liv) Treating gas and piston together as the system, p= 200 - 2005 100 kPa The assumptions remains Same. Now, Work , POV Ws (100103) * (0.04 10.4) 1600 3 = 1.6 kJ W= .. Work Done by = 1.6 kJ (v) 200 kPa Now, the gas and piston surrounding pressure, pa Work is done on the surrounding, therapie Work done will be negative -(2001 203) * (0.0480.4) this W = POV 1600 J = 1.6 ki :. Work Done by the surrounding = - 1.6 kJ (viz. Heat and work are two different types of energy in transit. Heat is due to temperature difference while work is the transfer of mechanical electrical etc. energy between two systems,