physics: Add kinetic energy mod

physics/src/kinetic_energy.rs

@@ -0,0 +1,38 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+//! Find the kinetic energy of an object, given its mass and velocity.
+//!
+//! [Kinetic energy](https://en.m.wikipedia.org/wiki/Kinetic_energy)
+
+/// Calculate kinetic energy.
+///
+/// The kinetic energy of a non-rotating object of mass m traveling at a speed v is ½mv²
+#[must_use]
+pub fn kinetic_energy(mass: f64, velocity: f64) -> f64 {
+    debug_assert!(mass >= 0.0);
+    0.5 * mass * velocity.abs() * velocity.abs()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::kinetic_energy;
+
+    #[test]
+    fn test_kinetic_energy() {
+        const PAIRS: &[(f64, f64, f64)] = &[
+            (10.0, 10.0, 500.0),
+            (0.0, 10.0, 0.0),
+            (10.0, 0.0, 0.0),
+            (20.0, -20.0, 4000.0),
+            (0.0, 0.0, 0.0),
+            (2.0, 2.0, 4.0),
+            (100.0, 100.0, 500000.0),
+        ];
+
+        for (mass, velocity, result) in PAIRS {
+            assert_eq!(kinetic_energy(*mass, *velocity), *result);
+        }
+    }
+}

physics/src/lib.rs

@@ -10,6 +10,7 @@
     clippy::pedantic
 )]
 
+pub mod kinetic_energy;
 pub mod potential_energy;
 pub mod shear_stress;
 pub mod speed_of_sound;