break & looping

[muhammad92]

why i did't get answet as :

Enter the launched velocity : 60
Projectile launched straight up at 60 m/s
Time <second>    Height <meters>

  0             0
  1             55.1
  2             100.4
  3             135.9
  4             161.6
  5             177.5
  6             183.6
  7             179.9
  8             166.4
  9             143.1
  10            110
  11            67.1
  12            14.4
  13            0.0

but like this? :

Enter the launched velocity : 60
Projectile launched straight up at 60 m/s
Time <second>    Height <meters>

  0             0
  1             55.1
  2             100.4
  3             135.9
  4             161.6
  5             177.5
  6             183.6
  7             179.9
  8             166.4
  9             143.1
  10            110
  11            67.1
  12            14.4
  13            -48.1

here is my code :

// height projectile

#include <iostream>
using namespace std;

int main()
{
	float v, h, g=9.8, t=0.0;

	cout<<"Enter the launched velocity : ";
	cin>>v;

	cout<<"\n\nProjectile launched straight up at "<<v<<" m/s"<<endl;
	cout<<"Time <second> \t Height <meters>"<<endl;
	
	while (h>=0)
	{
		h=(v*t)-((1.0/2.0)*g*t*t);
		cout<<"\n  "<<t<<"\t\t"<<h;
		t++;
		
	/*	if (h==0)
			{
				break;
			}
	*/
	}
	
	cout<<endl;
	system ("PAUSE");
	return 0;
}

[ResidentBiscuit]

Looks like you iterated just one too many times. Why not change it to (h>0) instead? It looks like you tried to do that in a backwards way, but did it after the calculation already happens.

[cire]

Well, obviously when h is less than 0, you've hit the ground. That should be a condition you handle in the calculation.

It's only luck the while condition executes at all. h is not initialized to anything before it is used.

If I were you, I would extract the code to calculate the height and stick it in it's own function. Maybe end up with something like:

// height projectile

#include <iostream>
using namespace std;

float calculateHeight( float initialVelocity, unsigned ticksPassed, float gravity )
{
    const float dist = initialVelocity * ticksPassed ;
    float height = dist - (1.0f/2.0f) * gravity * ticksPassed * ticksPassed ;
    return height < 0 ? 0 : height ;
}

int main()
{
    const float g = 9.8f ;
    float v ;

    cout<<"Enter the launched velocity : ";
    cin>>v;

    cout<<"\n\nProjectile launched straight up at "<<v<<" m/s"<<endl;
    cout<<"Time <second> \t Height <meters>"<<endl;

    std::cout << "  0\t\t0\n" ;  // 0 time is 0 height.

    float h ;
    unsigned t = 0 ;
    do	{
        h = calculateHeight(v, ++t, g) ;
        std::cout << "  " << t << "\t\t" << h << '\n' ;
    } while ( h > 0 ) ;

    cout<<endl;
    system ("PAUSE");
    return 0;
}