diff --git a/LPFP-core.cabal b/LPFP-core.cabal
--- a/LPFP-core.cabal
+++ b/LPFP-core.cabal
@@ -1,5 +1,5 @@
 name:           LPFP-core
-version:        1.1.1
+version:        1.1.5
 synopsis:       Code for the book Learn Physics with Functional Programming
 description:    Haskell code to help the user learn mechanics of one particle,
                 mechanics of multiple interacting particles, and electromagnetic theory.
@@ -36,5 +36,5 @@
       LPFPCore.Maxwell
   hs-source-dirs: src
   build-depends: base >= 4.7 && < 5,
-                 containers >= 0.6 && < 0.7
+                 containers >= 0.6 && < 0.8
   default-language: Haskell2010
diff --git a/src/LPFPCore/Mechanics1D.hs b/src/LPFPCore/Mechanics1D.hs
--- a/src/LPFPCore/Mechanics1D.hs
+++ b/src/LPFPCore/Mechanics1D.hs
@@ -106,7 +106,7 @@
 dampedHOStates :: [State1D]
 dampedHOStates = statesTXV 0.001 0.0027 (0.0,0.1,0.0) dampedHOForces
 
-pingpongPosition :: Time -> Velocity
+pingpongPosition :: Time -> Position
 pingpongPosition = positionFtxv 0.001 0.0027 (0,0.1,0) dampedHOForces
 
 pingpongVelocity :: Time -> Velocity
diff --git a/src/LPFPCore/Newton2.hs b/src/LPFPCore/Newton2.hs
--- a/src/LPFPCore/Newton2.hs
+++ b/src/LPFPCore/Newton2.hs
@@ -160,7 +160,7 @@
 pedalCoastAir2 :: Time -> Velocity
 pedalCoastAir2 = velocityFtv 0.1 20 (0,0)
                  [\( t,_v) -> pedalCoast t
-                 ,\(_t, v) -> fAir 1 1.225 0.5 v]
+                 ,\(_t, v) -> fAir 2 1.225 0.5 v]
 
 velocityCF' :: Mass
             -> Velocity          -- initial velocity