diff --git a/LPFP.cabal b/LPFP.cabal
--- a/LPFP.cabal
+++ b/LPFP.cabal
@@ -1,5 +1,5 @@
 name:           LPFP
-version:        1.1.4
+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.
@@ -35,7 +35,7 @@
   hs-source-dirs: src
   build-depends:
       base >= 4.7 && < 5,
-      containers >= 0.6.7 && < 0.7,
+      containers >= 0.6.7 && < 0.8,
       Vis >= 1.0.0 && < 1.1,
       diagrams-cairo >= 1.4.2 && < 1.5,
       diagrams-lib >= 1.4.6 && < 1.5,
diff --git a/src/LPFP/Mechanics1D.hs b/src/LPFP/Mechanics1D.hs
--- a/src/LPFP/Mechanics1D.hs
+++ b/src/LPFP/Mechanics1D.hs
@@ -117,7 +117,7 @@
                ,Key Nothing
                ] [(t,x) | (t,x,_) <- take 3000 dampedHOStates]
 
-pingpongPosition :: Time -> Velocity
+pingpongPosition :: Time -> Position
 pingpongPosition = positionFtxv 0.001 0.0027 (0,0.1,0) dampedHOForces
 
 dampedHOGraph2 :: IO ()
diff --git a/src/LPFP/Newton2.hs b/src/LPFP/Newton2.hs
--- a/src/LPFP/Newton2.hs
+++ b/src/LPFP/Newton2.hs
@@ -198,7 +198,7 @@
 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