You are making a classic mistake. REal physics do not corrolate to game physics. You will have to tweak the games gravity and mass so that things look and act like you want them to. In other words, don't focus on making your game gravity 9.8 m/s/s; rather tweak it in gamestudio until it looks and acts like you want it.

Also, remember to make ample use of the "time" variable to take variances in timeslices into account.