 So let's just do this one. It says a piston has a constant external pressure of 15.0 ATMs How much work has been done if the cylinder goes from a volume of point one five zero liters to point four eight zero liters and then another question it says in which direction does the work flow? So into the system or out of the system. Okay? So what do we have to remember? We've got to know the work PV equation. So work PV equals negative pressure external times the change in volume. You guys remember that? The change in volume of course is going to be Vf minus Vi. So we're going to have to look for these terms in order to figure out the work. So pressure external It gives us as 15.0 ATM and then it gives us the initial volume as zero point one five zero liters Okay, so in order to figure out the delta V All right, it's going to be 0.480 liters minus 0.150 liters 0.330 liters And then So it gives us the external pressure. So all we've got to do now Figure out the work So negative External pressure 15.0 ATM times the change in volume which is 0.330 liters. We've got negative 4.95 liter 18 So what you guys got? and then Remember leader ATM, I guess it's not always the best System are the best units to use for Energy transfer, so if you guys recall what the Conversion to Joules was So one liter ATM Equals 101.3 Joules right so let's convert it to Joules three three So negative 5.0.1 So that's how much work this is doing is it going out of the system or into it? How do you know? Negative okay, so negative is out of the system Positive is M2 Any questions on that one? I'll let you do those other two on your own maybe I'll do one with the Class this afternoon You can try the other one on your questions