diff --git a/class_materials/exercises/particle_update_position.ipynb b/class_materials/exercises/particle_update_position.ipynb
index b3d829a..3e67429 100644
--- a/class_materials/exercises/particle_update_position.ipynb
+++ b/class_materials/exercises/particle_update_position.ipynb
@@ -52,15 +52,19 @@
    ],
    "source": [
     "class Particle:\n",
-    "    def __init__(self, mass, velocity):\n",
+    "    def __init__(self, mass, velocity, position = 0):\n",
     "        self.mass = mass\n",
     "        self.velocity = velocity\n",
+    "        self.position = position\n",
     "\n",
     "    def momentum(self):\n",
     "        return self.mass * self.velocity\n",
     "\n",
-    "particle = Particle(mass=2.1, velocity=0.8)\n",
-    "print(particle.momentum())"
+    "    def update_position(self, dt):\n",
+    "        self.position = self.position + self.velocity * dt\n",
+    "\n",
+    "particle = Particle(mass=2.1, velocity=0.8, position = 8.2)\n",
+    "print(particle.momentum())\n"
    ]
   },
   {
@@ -84,10 +88,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {},
-   "outputs": [],
-   "source": []
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "8.28"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "particle.update_position(0.1)\n",
+    "particle.position"
+   ]
   },
   {
    "cell_type": "code",
@@ -118,7 +136,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.11"
+   "version": "3.13.6"
   },
   "toc": {
    "nav_menu": {
@@ -142,5 +160,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }