C++ Logic Issue - c++

Question

I'm trying to write a simple c++ program that outputs an objects current height once it hits a specific point. The object I'm trying to accomplish is that you have an object that starts at a varied position a moves off under a random velocity with gravity attached. If the ball collides with a wall or another object, it should move backward, with no energy loss, but still continue to fall due to gravity. Once the ball has reached a specific height, output that value.
Now, all I'm trying to do right now is check to see if my ball has gone beyond my width bounds. But for the life of me I can't see why my last if statement at the bottom wont call.
Am I missing / doing something really stupid?
int _tmain(int argc, _TCHAR* argv[])
{
float velocity;
float height, targetHeight;
float gravity;
float time;
float angle;
float width;
float move;
float distance;
gravity = 9.80f;
time = 0;
distance = 0;
cout << "Set Height\n";
cin >> height;
cout << "Set target height\n";
cin >> targetHeight;
cout << "Set Angle ( 0 - 90 ): \n";
cin >> angle;
angle *= 3.14 * 180; // convert to radians
cout << "Set velocity (0 - 100): \n";
cin >> velocity;
cout << "Set Play field Width: \n";
cin >> width;
while( height >= target )
{
time++;
distance += velocity * cos(angle) * time;
height += (velocity * sin(angle) * time) - (gravity * pow(time, 2) ) / 2;
}
if( distance == width)
{
cout << "You've hit the wall\n";
}
return 0;
}

Answer 1

Your final if statement if( distance == width ) does not test if the distance has gone beyond the width. You probably want if( distance >= width ). There doesn't appear to be any testing of distance traveled within your movement loop so distance could easily be greater than the width and thus cause your if to not be true.

Answer 2

Move backwards at the same speed: velocity = -velocity;. Of course, if it's moving backwards, it may hit the other wall, so you probably want to check the distance == 0; as well. (Since it's floating point, I would also suggest you use >= and <= instead of exact comparisons, or you may find that the ball was one micrometer PAST the wall and then continues until it hits the sun, or you run out of math, or whatever else happens if you keep going forever).
I would further suggest that you would need the width and breadth of the "room" the ball is bouncing around in. So, in total you need X, Y, and Z coordinates of the ball.

Answer 3

Note: your time ever increases, which implies a direct formula for height and distance (one saying distance = f(time);), but you're accumulating.
So probably you want to assign instead of increment your distance and height variables:
distance = velocity * cos(angle) * time;
height = (velocity * sin(angle) * time) - (gravity * pow(time, 2) ) / 2;
Next to that, you probably want to check whether the travelled distance exceeds the distance to the wall (equality with floats is very improbable, plus inaccurate).
Some stylistic advice: put those equations in functions of their own.