c programming - issue with projectile motion ( calculating hieght and range )

[Khaoula Ali]

well I am not familliar with c programming so it will be so great if anyone could help me
actually I've been asked to write a program which include :

2- In kinetics, we often study projetiles. You are asked to write a program that:
1- prompts the user to enter the magnitude of the initial velocity and the angle it makes with respect to the horizontal axis in DEGREEs.
2- Calculates and displays the range of the projectile, the maximum height it reaches. 3- displays the function of the path y(x).
4- calculates the height at any given point 0<x<range;

We assume that:
-There is no acceleration along the horizontal axis.
-The acceleration along the y axis is the gravity ( g=9.81m/s²)
-The projectile is considered to be a point object and at t=0 x=0 y=0.





and then I've written this and the pb was when I put v0 and theta the range and the hight is 00

 
#include <stdio.h>
#include <conio.h>
#include <math.h>
float v0,x,y,os,h;
float theta;
float g = 9.81;
int main()
{
    printf("Enter the magnitude of v0:\n");
    scanf("%f",&v0);
    printf("Enter theta in degree:\n");
    scanf("%d",&theta);
    os = (v0*v0)*sin(2*(theta))/9.81;
    printf("%f\n",os);
    h = sqrt(v0*sin(theta))/(2*9.81);
    printf("%f\n",h);
    printf("y=(tan(theta)*(x))-((0.5*g*x)/(v0*cos(theta)))\n");
    getch();
    return 0;
}

[anduril462]

Global variables are bad. You should move all of those variable declarations inside main. Also, scanf("%d",&theta); is wrong. What is the type of theta? What is the correct format specifier for a float?

[hk_mp5kpdw]

The trigonometric functions in C take radians as input. Your degree value therefore needs to be first converted to radians (multiply by PI and divide by 180 I believe) before being used as input to those functions.

[caroundw5h]

remove

<conio.h>

as it's a non standard header. As well remove your call to

getche()

and simply call

getchar();

you may need a few more calls to getchar() - i haven't ran your code - or since you're on windows some IDE will set it so once your code is finished, it will wait for input before terminating the program.