diff --git a/OGP1718-Worms/src/worms/model/Projectile.java b/OGP1718-Worms/src/worms/model/Projectile.java
index 9b1dac7..7f35a7b 100644
--- a/OGP1718-Worms/src/worms/model/Projectile.java
+++ b/OGP1718-Worms/src/worms/model/Projectile.java
@@ -66,9 +66,20 @@ public abstract class Projectile extends GameObject {
 
 	public Coordinate getJumpStep(double elapsedTime) {
 		// TODO zie naar worm hoe dit moet, implementatie moet wel anders!
+		if (Double.isNaN(elapsedTime) || elapsedTime > this.getJumpTime(jumpTimeStep) || elapsedTime < 0)
+			throw new IllegalArgumentException();
+		
+		double velocity = this.jumpVelocity();
+		
+		
+		
 		return null;
 	}
 
+	public double jumpVelocity() {
+		return -1;
+	}
+	
 	public double getJumpTime(double jumpTimeStep) {
 
 		// TODO zie naar worm hoe dit moet, implementatie moet wel anders!