Bouncing Ball

[INF3RN0666]

HEY EVERYBODY!

I'm trying to make a soccer 2D game for someone and there's a problem with the physics i'm trying to implement. (Too bad we don't learnt how to implement physics equations into code at school!) I wan't to make a ball that bounces like a normal ball in real life. So with friction, and gravity so that it doesn't keep bouncing for ever! I also want to make it so that when one of the players applies a force onto it, I want it to fly like a ball does when you head it! Any ideas? What equations must I use and how must I implement them? THANK YOU!

[alkatran]

Here is all you need:

Acceleration of gravity: 9.8 m/s/s

All you need:
(m = metres, s = seconds, kg = kilogrammes (weight))
Distance - m
Speed - m/s
Acceleration - m/s/s
Time - s
Newtons (Force) m/s/s*kg
Friction = F (force that the object is being applied to the surface by (usually 9.8(gravity)*kg)) * X (amount of friction from the surface)
F*X, easy enough right? So if you have a 2 kg ball that starts 5m above the playing field, going 5m/s (no accel on horizontal) how fast will it be going after the first bounce?
X = on x axis, I = initial, F = final

D = 5
S(x) = 5
S(yi) = 0
S(Yf) = ? : -9.9
A(x) = 0
A(y) = -9.8
T = ? :: 1.01
F(yi) = -9.8 * 2 = -19.6
F(yf) = ?
Fric = -9.8 * 2 = -19.6


A few equations...
S(f)^2 = S(i)^2 + 2*A*D so to find the final Y speed:
X^2 = 0^2 + 2*-9.8*5=-98
sqr(x^2) = sqr(-98) = -9.9 (that'll give an error, do Sqr(98)*-1)


Now since speed is m/s and distance is m, you can isolate S for the time (you want the AVERAGE speed):
T = D / [ (S(i) + S(f) ) / 2 ]
X = 5 / [(0 + -9.9)/2] = -1.01 (obviously this won't be negative, so change it to 1.01)
Note that you don't really need the time here

So, the final speed is when the ball HITS the ground. Now assuming this ball defies a few laws... such as staying on the ground for more then .00000000000000001 seconds...

Answer = S(f) - 19.8
Now remember that friction can't let you put the speed below 0, so the answer is 0.

Note that: In most games gravity isn't as high as 9.8 and grass won't have a friction of 2.



That concludes your 5 minute physics class. Ask away.

[vbNeo]

Really basic physics, but a nice way of putting it - thanks!