Example: Calculate Weight on Different Celestial Bodies in C

// Calculate Weight on Different Celestial Bodies
#include <stdio.h>

// Define gravitational accelerations for various celestial bodies (in m/s^2)
#define GRAVITY_EARTH     9.81
#define GRAVITY_MOON      1.62
#define GRAVITY_MARS      3.71
#define GRAVITY_JUPITER  24.79

int main() {
    float mass;
    float gravity;
    float weight;
    int choice;

    // Step 1: Prompt user for mass input
    printf("Please enter the object's mass in kilograms (kg): ");
    if (scanf("%f", &mass) != 1 || mass < 0) {
        printf("Invalid input. Please enter a non-negative number for mass.\n");
        return 1;
    }

    // Step 2: Present options for celestial bodies
    printf("\nSelect a celestial body to calculate weight on:\n");
    printf("1. Earth (g = %.2f m/s^2)\n", GRAVITY_EARTH);
    printf("2. Moon (g = %.2f m/s^2)\n", GRAVITY_MOON);
    printf("3. Mars (g = %.2f m/s^2)\n", GRAVITY_MARS);
    printf("4. Jupiter (g = %.2f m/s^2)\n", GRAVITY_JUPITER);
    printf("Enter your choice (1-4): ");
    
    // Step 3: Read user's choice and set gravity accordingly
    if (scanf("%d", &choice) != 1 || choice < 1 || choice > 4) {
        printf("Invalid choice. Please enter a number between 1 and 4.\n");
        return 1;
    }

    switch (choice) {
        case 1: gravity = GRAVITY_EARTH;   printf("Calculating weight on Earth...\n");   break;
        case 2: gravity = GRAVITY_MOON;    printf("Calculating weight on Moon...\n");    break;
        case 3: gravity = GRAVITY_MARS;    printf("Calculating weight on Mars...\n");    break;
        case 4: gravity = GRAVITY_JUPITER; printf("Calculating weight on Jupiter...\n"); break;
        default: // This case should ideally not be reached due to prior validation
                 printf("An unexpected error occurred.\n");
                 return 1;
    }

    // Step 4: Calculate weight using the formula W = m * g
    weight = mass * gravity;

    // Step 5: Display the calculated mass and weight for the chosen body
    printf("The mass of the object is: %.2f kg\n", mass);
    printf("The weight of the object is: %.2f N\n", weight);

    return 0;
}