Added GroundToGroundProjectileMotion (#6714)

* Added GroundToGroundProjectileMotion * Fix checkstyle issues. * Fix checkstyle issues.
2025-12-19 07:00:35 +08:00 · 2025-10-09 12:53:58 +05:30
parent e22ce0005e
commit b1aa896e17
2 changed files with 239 additions and 0 deletions
--- a/src/main/java/com/thealgorithms/physics/GroundToGroundProjectileMotion.java
+++ b/src/main/java/com/thealgorithms/physics/GroundToGroundProjectileMotion.java
@@ -0,0 +1,90 @@
+package com.thealgorithms.physics;
+
+/**
+ * Ground to ground projectile motion calculator
+ *
+ * Ground to ground projectile motion is when a projectile's trajectory
+ * starts at the ground, reaches the apex, then falls back on the ground.
+ *
+ * @author [Yash Rajput](https://github.com/the-yash-rajput)
+ */
+public final class GroundToGroundProjectileMotion {
+
+    private GroundToGroundProjectileMotion() {
+        throw new AssertionError("No instances.");
+    }
+
+    /** Standard gravity constant (m/s^2) */
+    private static final double GRAVITY = 9.80665;
+
+    /**
+     * Convert degrees to radians
+     *
+     * @param degrees Angle in degrees
+     * @return Angle in radians
+     */
+    private static double degreesToRadians(double degrees) {
+        return degrees * (Math.PI / 180.0);
+    }
+
+    /**
+     * Calculate the time of flight
+     *
+     * @param initialVelocity The starting velocity of the projectile (m/s)
+     * @param angle The angle that the projectile is launched at in degrees
+     * @return The time that the projectile is in the air for (seconds)
+     */
+    public static double timeOfFlight(double initialVelocity, double angle) {
+        return timeOfFlight(initialVelocity, angle, GRAVITY);
+    }
+
+    /**
+     * Calculate the time of flight with custom gravity
+     *
+     * @param initialVelocity The starting velocity of the projectile (m/s)
+     * @param angle The angle that the projectile is launched at in degrees
+     * @param gravity The value used for the gravity constant (m/s^2)
+     * @return The time that the projectile is in the air for (seconds)
+     */
+    public static double timeOfFlight(double initialVelocity, double angle, double gravity) {
+        double viy = initialVelocity * Math.sin(degreesToRadians(angle));
+        return 2.0 * viy / gravity;
+    }
+
+    /**
+     * Calculate the horizontal distance that the projectile travels
+     *
+     * @param initialVelocity The starting velocity of the projectile (m/s)
+     * @param angle The angle that the projectile is launched at in degrees
+     * @param time The time that the projectile is in the air (seconds)
+     * @return Horizontal distance that the projectile travels (meters)
+     */
+    public static double horizontalRange(double initialVelocity, double angle, double time) {
+        double vix = initialVelocity * Math.cos(degreesToRadians(angle));
+        return vix * time;
+    }
+
+    /**
+     * Calculate the max height of the projectile
+     *
+     * @param initialVelocity The starting velocity of the projectile (m/s)
+     * @param angle The angle that the projectile is launched at in degrees
+     * @return The max height that the projectile reaches (meters)
+     */
+    public static double maxHeight(double initialVelocity, double angle) {
+        return maxHeight(initialVelocity, angle, GRAVITY);
+    }
+
+    /**
+     * Calculate the max height of the projectile with custom gravity
+     *
+     * @param initialVelocity The starting velocity of the projectile (m/s)
+     * @param angle The angle that the projectile is launched at in degrees
+     * @param gravity The value used for the gravity constant (m/s^2)
+     * @return The max height that the projectile reaches (meters)
+     */
+    public static double maxHeight(double initialVelocity, double angle, double gravity) {
+        double viy = initialVelocity * Math.sin(degreesToRadians(angle));
+        return Math.pow(viy, 2) / (2.0 * gravity);
+    }
+}
--- a/src/test/java/com/thealgorithms/physics/GroundToGroundProjectileMotionTest.java
+++ b/src/test/java/com/thealgorithms/physics/GroundToGroundProjectileMotionTest.java
@@ -0,0 +1,149 @@
+package com.thealgorithms.physics;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+/**
+ * JUnit test class for GroundToGroundProjectileMotion
+ *
+ * Contains unit tests for projectile motion calculations using JUnit 5
+ */
+public class GroundToGroundProjectileMotionTest {
+
+    private static final double EPSILON = 0.001; // Tolerance for floating point comparison
+
+    @Test
+    @DisplayName("Test time of flight calculation")
+    public void testTimeOfFlight() {
+        // Arrange
+        double initialVelocity = 5.0;
+        double angle = 40.0;
+        double expectedTimeOfFlight = 0.655;
+
+        // Act
+        double flightTimeOutput = GroundToGroundProjectileMotion.timeOfFlight(initialVelocity, angle);
+        flightTimeOutput = Math.round(flightTimeOutput * 1000.0) / 1000.0;
+
+        // Assert
+        assertEquals(expectedTimeOfFlight, flightTimeOutput, EPSILON, "Time of flight should be " + expectedTimeOfFlight + " seconds");
+
+        System.out.println("Projectile Flight Time Test");
+        System.out.println("Input Initial Velocity: " + initialVelocity + " m/s");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Expected Output: " + expectedTimeOfFlight + " seconds");
+        System.out.println("Actual Output: " + flightTimeOutput + " seconds");
+        System.out.println("TEST PASSED\n");
+    }
+
+    @Test
+    @DisplayName("Test horizontal range calculation")
+    public void testHorizontalRange() {
+        // Arrange
+        double initialVelocity = 5.0;
+        double angle = 40.0;
+        double flightTime = 0.655;
+        double expectedHorizontalRange = 2.51;
+
+        // Act
+        double horizontalRangeOutput = GroundToGroundProjectileMotion.horizontalRange(initialVelocity, angle, flightTime);
+        horizontalRangeOutput = Math.round(horizontalRangeOutput * 100.0) / 100.0;
+
+        // Assert
+        assertEquals(expectedHorizontalRange, horizontalRangeOutput, EPSILON, "Horizontal range should be " + expectedHorizontalRange + " meters");
+
+        System.out.println("Projectile Horizontal Range Test");
+        System.out.println("Input Initial Velocity: " + initialVelocity + " m/s");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Input Time Of Flight: " + flightTime + " seconds");
+        System.out.println("Expected Output: " + expectedHorizontalRange + " meters");
+        System.out.println("Actual Output: " + horizontalRangeOutput + " meters");
+        System.out.println("TEST PASSED\n");
+    }
+
+    @Test
+    @DisplayName("Test max height calculation")
+    public void testMaxHeight() {
+        // Arrange
+        double initialVelocity = 5.0;
+        double angle = 40.0;
+        double expectedMaxHeight = 0.527; // Updated to match actual calculation
+
+        // Act
+        double maxHeightOutput = GroundToGroundProjectileMotion.maxHeight(initialVelocity, angle);
+        maxHeightOutput = Math.round(maxHeightOutput * 1000.0) / 1000.0;
+
+        // Assert
+        assertEquals(expectedMaxHeight, maxHeightOutput, EPSILON, "Max height should be " + expectedMaxHeight + " meters");
+
+        System.out.println("Projectile Max Height Test");
+        System.out.println("Input Initial Velocity: " + initialVelocity + " m/s");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Expected Output: " + expectedMaxHeight + " meters");
+        System.out.println("Actual Output: " + maxHeightOutput + " meters");
+        System.out.println("TEST PASSED\n");
+    }
+
+    @Test
+    @DisplayName("Test time of flight with custom gravity")
+    public void testTimeOfFlightWithCustomGravity() {
+        // Arrange
+        double initialVelocity = 10.0;
+        double angle = 45.0;
+        double customGravity = 1.62; // Moon gravity (m/s^2)
+
+        // Act
+        double flightTime = GroundToGroundProjectileMotion.timeOfFlight(initialVelocity, angle, customGravity);
+
+        // Assert
+        assertTrue(flightTime > 0, "Flight time should be positive");
+        assertTrue(flightTime > 8.0, "Flight time on moon should be longer than on Earth");
+
+        System.out.println("Custom Gravity Test (Moon)");
+        System.out.println("Input Initial Velocity: " + initialVelocity + " m/s");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Gravity: " + customGravity + " m/s^2");
+        System.out.println("Flight Time: " + flightTime + " seconds");
+        System.out.println("TEST PASSED\n");
+    }
+
+    @Test
+    @DisplayName("Test projectile at 90 degrees (straight up)")
+    public void testVerticalProjectile() {
+        // Arrange
+        double initialVelocity = 20.0;
+        double angle = 90.0;
+
+        // Act
+        double horizontalRange = GroundToGroundProjectileMotion.horizontalRange(initialVelocity, angle, 1.0);
+
+        // Assert
+        assertEquals(0.0, horizontalRange, EPSILON, "Horizontal range should be zero for vertical launch");
+
+        System.out.println("Vertical Projectile Test");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Horizontal Range: " + horizontalRange + " meters");
+        System.out.println("TEST PASSED\n");
+    }
+
+    @Test
+    @DisplayName("Test projectile at 0 degrees (horizontal)")
+    public void testHorizontalProjectile() {
+        // Arrange
+        double initialVelocity = 15.0;
+        double angle = 0.0;
+
+        // Act
+        double maxHeight = GroundToGroundProjectileMotion.maxHeight(initialVelocity, angle);
+
+        // Assert
+        assertEquals(0.0, maxHeight, EPSILON, "Max height should be zero for horizontal launch");
+
+        System.out.println("Horizontal Projectile Test");
+        System.out.println("Input Angle: " + angle + " degrees");
+        System.out.println("Max Height: " + maxHeight + " meters");
+        System.out.println("TEST PASSED\n");
+    }
+}