diff --git a/src/c/funktionen.c b/src/c/funktionen.c
index d6cb83d..ba2978e 100644
--- a/src/c/funktionen.c
+++ b/src/c/funktionen.c
@@ -119,4 +119,8 @@ int i(int v, int r) {
 
 int p(int f, int a) {
     return f / a;
+}
+
+float f(float m) {
+    return m * 9.81;
 }
\ No newline at end of file
diff --git a/src/test/test_funktionen.c b/src/test/test_funktionen.c
index e73a405..a03c572 100644
--- a/src/test/test_funktionen.c
+++ b/src/test/test_funktionen.c
@@ -257,4 +257,18 @@ void test_pressure_at_force360_area12(void)
     TEST_ASSERT_EQUAL_INT(expected, actual);
 }
 
+void test_weight_at_mass100(void)
+{
+    /* arrange */
+    float actual;
+    float expected = 981;
+
+    /* act */;
+    float m = 100;
+    actual = f(m);
+
+    /* assert */
+    TEST_ASSERT_EQUAL_FLOAT(expected, actual);
+}
+
 #endif
\ No newline at end of file