diff --git a/src/Acceleration.java b/src/Acceleration.java
index 3bccc68..37babc8 100644
--- a/src/Acceleration.java
+++ b/src/Acceleration.java
@@ -1,25 +1,30 @@
-import java.util.*;
-
 public class Acceleration {
 	private double mass;
-	private Map.Entry<Double, Double> force;
+	private Pair<Double> force;
 	private Velocity velocity;
 	private Onground onground;
-	private Map.Entry<Double, Double> acceleration;
+	private Pair<Double> acceleration;
+
 	public void updateMass(double mass) {
 		this.mass = mass;
-		acceleration = (this.onground.getOnground() ? new AbstractMap.SimpleEntry<>((force.getKey()/mass), 0.0) : new AbstractMap.SimpleEntry<>((force.getKey()/mass), (force.getValue()/mass)));
+		acceleration = (this.onground.getOnground() ? new Pair<>((force.getX() / mass), 0.0)
+				: new Pair<>((force.getX() / mass), (force.getY() / mass)));
 		velocity.updateAcceleration(acceleration);
 	}
-	public void updateForce(Map.Entry<Double, Double> force) {
+
+	public void updateForce(Pair<Double> force) {
 		this.force = force;
-		acceleration = (this.onground.getOnground() ? new AbstractMap.SimpleEntry<>((force.getKey()/mass), 0.0) : new AbstractMap.SimpleEntry<>((force.getKey()/mass), (force.getValue()/mass)));
+		acceleration = (this.onground.getOnground() ? new Pair<>((force.getX() / mass), 0.0)
+				: new Pair<>((force.getX() / mass), (force.getY() / mass)));
 		velocity.updateAcceleration(acceleration);
 	}
+
 	public Acceleration(Velocity velocity, Onground onground) {
+		this.velocity = velocity;
 		this.onground = onground;
 	}
-	public Map.Entry<Double, Double> getAcceleration() {
+
+	public Pair<Double> getAcceleration() {
 		return acceleration;
 	}
 }
\ No newline at end of file