2008BAP 1 Solutions

# 8 m s2 300 m 1 2 2 10 103 kg m 3 224

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 2 For correctly accounting for atmospheric pressure (with no obvious algebraic errors) leading to an answer P0 is atmospheric pressure, and Pp = P0 + Pgauge + Pgauge = Pp - P0 = 3.16 10 4 Pa (or 3.23 10 4 Pa using g = 10 m s2 ) ( )( ) ) 1 point 1 point 2008 The College Board. All rights reserved. Visit the College Board on the Web: www.collegeboard.com. AP PHYSICS B 2008 SCORING GUIDELINES Question 5 10 points total Distribution of points (a) 3 points Process A B B C C A W 0 - + Q + + - DU + 0 - 1 point 1 point 1 point For correctly identifying the signs of all three variables (W , DU , Q ) for process A B For correctly identifying the signs of all three variables (W , DU , Q ) for process B C For correctly identifying the signs of all three variables (W , DU , Q ) for process C A (b) 4 points For a correct explanation of why zero work is done on the gas Examples of correct responses include: There is no area under the graph/curve. There is no volume change. The piston does not move. W = - P DV , where DV = 0 . W = 0 by definition in an isochoric/isovolumetric process. For a correct explanation of why DU is positive Examples of correct responses include: For a fixed number of moles of a sample, an increase in pressure at constant volume implies an increase in temperature, and an increased temperature implies an increase in internal energy ( DU is positive). State B is on a higher isotherm than state A. 3 U = nRT ; since T increases, DU is positive. 2 U = 3 PV ; since P increases at a constant V, DU is positive. 2 1 point 1 point A correct use of the first law of thermodynamics leading to DU being positive ( DU = Q + W , but W = 0 so DU = Q ; since Q is positive, DU must be also). For a correct explanation of why Q is positive Examples of correct responses include: If pressure increases and volume is constant, heat must be added to system. If temperature increases and volume is constant, heat must be added to system. A correct use of the first law of thermodynamics leading to Q being positive ( DU = Q + W , but W = 0 so DU = Q ;...
View Full Document

## This note was uploaded on 02/09/2011 for the course PHYS 10 taught by Professor Davidnewton during the Spring '11 term at DeAnza College.

Ask a homework question - tutors are online