diff --git a/js/common/model/Particle.ts b/js/common/model/Particle.ts
index 5dfa2d4e..0c2779f8 100644
--- a/js/common/model/Particle.ts
+++ b/js/common/model/Particle.ts
@@ -167,18 +167,12 @@ export default class Particle {
 
   public get vy(): number { return this._vy; }
 
-  /**
-   * Gets the particle's speed, the velocity magnitude, in pm/ps.
-   */
-  public get speed(): number {
-    return Math.sqrt( this._vx * this._vx + this._vy * this._vy );
-  }
-
   /**
    * Gets the kinetic energy of this particle, in AMU * pm^2 / ps^2.
    */
   public getKineticEnergy(): number {
-    return 0.5 * this._mass * this.speed * this.speed; // KE = (1/2) * m * |v|^2
+    const speed = this.getSpeed();
+    return 0.5 * this._mass * speed * speed; // KE = (1/2) * m * |v|^2
   }
 
   /**
@@ -228,11 +222,18 @@ export default class Particle {
   }
 
   /**
-   * Sets this particle's speed (velocity magnitude).
+   * Gets the particle's speed (velocity magnitude) in pm/ps.
+   */
+  public getSpeed(): number {
+    return Math.sqrt( this._vx * this._vx + this._vy * this._vy );
+  }
+
+  /**
+   * Sets this particle's speed (velocity magnitude) in pm/ps.
    */
   public setSpeed( speed: number ): void {
     assert && assert( speed >= 0, `invalid magnitude: ${speed}` );
-    this.scaleVelocity( speed / this.speed );
+    this.scaleVelocity( speed / this.getSpeed() );
   }
 
   /**
diff --git a/js/energy/model/AverageSpeedModel.ts b/js/energy/model/AverageSpeedModel.ts
index 7de3fc1f..c88f7497 100644
--- a/js/energy/model/AverageSpeedModel.ts
+++ b/js/energy/model/AverageSpeedModel.ts
@@ -184,7 +184,7 @@ function getAverageSpeed( particles: Particle[] ): number {
   if ( particles.length > 0 ) {
     let totalSpeed = 0;
     for ( let i = particles.length - 1; i >= 0; i-- ) {
-      totalSpeed += particles[ i ].speed;
+      totalSpeed += particles[ i ].getSpeed();
     }
     averageSpeed = totalSpeed / particles.length;
   }
diff --git a/js/energy/model/HistogramsModel.ts b/js/energy/model/HistogramsModel.ts
index f7dd9e5b..9743fc35 100644
--- a/js/energy/model/HistogramsModel.ts
+++ b/js/energy/model/HistogramsModel.ts
@@ -306,7 +306,7 @@ export default class HistogramsModel {
 function getSpeedValues( particles: Particle[] ): number[] {
   const values = [];
   for ( let i = particles.length - 1; i >= 0; i-- ) {
-    values.push( particles[ i ].speed );
+    values.push( particles[ i ].getSpeed() );
   }
   return values;
 }