diff --git a/js/ISLCA11yStrings.js b/js/ISLCA11yStrings.js
index 00f83b9..4b370ac 100644
--- a/js/ISLCA11yStrings.js
+++ b/js/ISLCA11yStrings.js
@@ -7,14 +7,15 @@ define( require => {
   const inverseSquareLawCommon = require( 'INVERSE_SQUARE_LAW_COMMON/inverseSquareLawCommon' );
 
   const ISLCA11yStrings = {
+    // TODO: replace instances of {{objectValueUnits}} or {{valueAndUnits}} to {{value}} {{units}}
 
     /***************************
      * Summary Pattern Strings *
      ***************************/
-    vectorSizePattern: {
+    summaryVectorSizePattern: {
       value: 'Force vectors are {{size}}.'
     },
-    vectorSizeValueUnitsPattern: {
+    summaryVectorSizeValueUnitsPattern: {
       value: 'Force vectors are {{size}} at {{objectValueUnits}}.'
     },
     robotPullSummaryPattern: {
@@ -90,15 +91,24 @@ define( require => {
     /************************
      * Force vector strings *
      ************************/
-    forceVectorsSize: {
+    forceVectorSizePattern: {
       value: 'Force vectors {{size}}.'
     },
-    vectorAlertNoValuePattern: {
+    vectorSizeForcesValuePattern: {
+      value: 'Vectors {{size}}, forces {{valueAndUnits}}.'
+    },
+    vectorSizePattern: {
       value: 'Vectors {{changeOrSize}}.'
     },
-    vectorAlertWithValuePattern: {
+    vectorSizeForcesNowValuePattern: {
       value: 'Vectors {{changeOrSize}}, forces now {{valueAndUnits}}.'
     },
+    getBigger: {
+      value: 'get bigger'
+    },
+    getSmaller: {
+      value: 'get smaller'
+    },
 
     /**********************
      * Qualitative Values *
diff --git a/js/view/ISLCObjectNode.js b/js/view/ISLCObjectNode.js
index c685553..476ebbb 100644
--- a/js/view/ISLCObjectNode.js
+++ b/js/view/ISLCObjectNode.js
@@ -33,6 +33,8 @@ define( function( require ) {
   var SimpleDragHandler = require( 'SCENERY/input/SimpleDragHandler' );
   var Tandem = require( 'TANDEM/Tandem' );
   var Util = require( 'DOT/Util' );
+  var Utterance = require( 'SCENERY_PHET/accessibility/Utterance' );
+  var utteranceQueue = require( 'SCENERY_PHET/accessibility/utteranceQueue' );
 
   // phetio
   var BooleanProperty = require( 'AXON/BooleanProperty' );
@@ -85,7 +87,7 @@ define( function( require ) {
    * @param {Object} options
    * @constructor
    */
-  function ISLCObjectNode( model, object, layoutBounds, modelViewTransform, pullForceRange, options ) {
+  function ISLCObjectNode( model, object, layoutBounds, stringManager, modelViewTransform, pullForceRange, options ) {
 
     var self = this;
 
@@ -294,7 +296,11 @@ define( function( require ) {
 
     this.redrawForce();
 
+    // a11y - for experimenting with default step sizes. Ignore if not explicitly set
     var defaultStepSize = QueryStringMachine.containsKey( 'stepSize' ) ? ISLCQueryParameters.stepSize : options.snapToNearest * 2;
+
+    var currentPosition = object.positionProperty.get();
+    var currentForce = model.forceProperty.get();
     var accessibleSliderOptions = {
       keyboardStep: defaultStepSize,
       shiftKeyboardStep: options.snapToNearest,
@@ -306,10 +312,34 @@ define( function( require ) {
       },
       startDrag: function() {
         object.isDragging = true;
+        currentPosition = object.positionProperty.get();
+        currentForce = model.forceProperty.get();
       },
       endDrag: function() {
+        var newPosition = object.positionProperty.get();
+        var newForce = model.forceProperty.get();
+        var forceGrowing = ( newForce - currentForce ) > 0;
+        var positionChanged = newPosition - currentPosition;
         object.isDragging = false;
         self.redrawForce();
+
+        // TODO: consider implementing with alertManager
+        // alertManager.positionSliderAlert( positionChanged );
+        if ( positionChanged ) {
+          // alert force vectors changed
+          // TODO: consider setting forceGrowing in ISLCStringManager
+          utteranceQueue.addToBack( new Utterance( {
+            alert: stringManager.getForceVectorsChangedAlertText( forceGrowing ),
+            uniqueGroupId: 'forceVectorChanged'
+          } ) );
+        }
+        else {
+          // alert state of force vectors
+          utteranceQueue.addToBack( new Utterance( {
+            alert: stringManager.getForceVectorStateAlertText(),
+            uniqueGroupId: 'forceVectorState'
+          } ) );
+        }
       },
       createAriaValueText: options.createAriaValueText
     };
diff --git a/js/view/ISLCStringManager.js b/js/view/ISLCStringManager.js
index 34917f8..65dd58c 100644
--- a/js/view/ISLCStringManager.js
+++ b/js/view/ISLCStringManager.js
@@ -18,23 +18,24 @@ define( require => {
   const unitsMetersString = require( 'string!INVERSE_SQUARE_LAW_COMMON/units.meters' );
   const unitsNewtonsString = require( 'string!INVERSE_SQUARE_LAW_COMMON/units.newtons' );
 
-  const vectorSizePatternString = ISLCA11yStrings.vectorSizePattern.value;
-  const vectorSizeValueUnitsPatternString = ISLCA11yStrings.vectorSizeValueUnitsPattern.value;
+  const summaryVectorSizePatternString = ISLCA11yStrings.summaryVectorSizePattern.value;
+  const summaryVectorSizeValueUnitsPatternString = ISLCA11yStrings.summaryVectorSizeValueUnitsPattern.value;
   const summaryInteractionHintPatternString = ISLCA11yStrings.summaryInteractionHintPattern.value;
   const distanceAndValueSummaryPatternString = ISLCA11yStrings.distanceAndValueSummaryPattern.value;
   const robotPullSummaryPatternString = ISLCA11yStrings.robotPullSummaryPattern.value;
   const robotPushSummaryPatternString = ISLCA11yStrings.robotPushSummaryPattern.value;
 
+  const vectorSizePatternString = ISLCA11yStrings.vectorSizePattern.value;
+  const forceVectorSizePatternString = ISLCA11yStrings.forceVectorSizePattern.value;
+  const vectorSizeForcesValuePatternString = ISLCA11yStrings.vectorSizeForcesValuePattern.value;
+  const vectorSizeForcesNowValuePatternString = ISLCA11yStrings.vectorSizeForcesNowValuePattern.value;
+
   // sphere strings
-  // const spherePositionHelpTextString = ISLCA11yStrings.spherePositionHelpText.value;
   const forceVectorMagnitudePatternString = ISLCA11yStrings.forceVectorMagnitudePattern.value;
   const forceAndVectorPatternString = ISLCA11yStrings.forceAndVectorPattern.value;
   const positionMeterMarkPatternString = ISLCA11yStrings.positionMeterMarkPattern.value;
   const objectLabelPositionPatternString = ISLCA11yStrings.objectLabelPositionPattern.value;
-  // const spherePositionProgressObjectPatternString = ISLCA11yStrings.spherePositionProgressObjectPattern.value;
-  // const spherePositionProgressPatternString = ISLCA11yStrings.spherePositionProgressPattern.value;
   const spherePositionRegionObjectPatternString = ISLCA11yStrings.spherePositionRegionObjectPattern.value;
-  // const spherePositionRegionPatternString = ISLCA11yStrings.spherePositionRegionPattern.value;
 
   /* new from 12/11/18 */
   const positionDistanceFromOtherObjectPatternString = ISLCA11yStrings.positionDistanceFromOtherObjectPattern.value;
@@ -42,6 +43,9 @@ define( require => {
   const distanceFromOtherObjectPatternString = ISLCA11yStrings.distanceFromOtherObjectPattern.value;
   const lastStopDistanceFromOtherObjectPatternString = ISLCA11yStrings.lastStopDistanceFromOtherObjectPattern.value;
 
+  const getBiggerString = ISLCA11yStrings.getBigger.value;
+  const getSmallerString = ISLCA11yStrings.getSmaller.value;
+
   const tinyString = ISLCA11yStrings.tiny.value;
   const verySmallString = ISLCA11yStrings.verySmall.value;
   const smallString = ISLCA11yStrings.small.value;
@@ -221,8 +225,8 @@ define( require => {
     getForceVectorsSummaryText() {
       const fillObject = {};
       const pattern = this.model.forceValuesProperty.get() ?
-                      vectorSizeValueUnitsPatternString :
-                      vectorSizePatternString;
+                      summaryVectorSizeValueUnitsPatternString :
+                      summaryVectorSizePatternString;
 
       fillObject.size = this.getForceVectorSize();
 
@@ -253,6 +257,34 @@ define( require => {
       return StringUtils.fillIn( pattern, { effort } );
     }
 
+    getForceVectorsChangedAlertText( vectorsGrowing ) {
+      const changeOrSize = vectorsGrowing ? getBiggerString : getSmallerString;
+      const valueAndUnits = this.getForceValueText();
+      const fillObject = { changeOrSize };
+
+      let pattern = vectorSizePatternString;
+
+      if ( this.model.forceValuesProperty.get() ) {
+        pattern = vectorSizeForcesNowValuePatternString;
+        fillObject.valueAndUnits = valueAndUnits;
+      }
+
+      return StringUtils.fillIn( pattern, fillObject );
+    }
+
+    getForceVectorStateAlertText() {
+      const size = this.getForceVectorSize();
+      const fillObject = { size };
+      let pattern = forceVectorSizePatternString;
+
+      if ( this.model.forceValuesProperty.get() ) {
+        pattern = vectorSizeForcesValuePatternString;
+        fillObject.valueAndUnits = this.getForceValueText();
+      }
+
+      return StringUtils.fillIn( pattern, fillObject );
+    }
+
     // TODO: string usage
     getPositionFocusAlertText() {
       const pattern = 'Force vectors {{size}}';