Blender Game Engine - Jumping help for 2.76 so I am trying to make a 2D platformer game, but I can not get the jumping right at all. I have tried using Linear Velocity, but all that does is jump slowly and I can't seem to speed it up and have full control over the physics. 

What I am trying to do is make a jump using Dynamics in the game engine that will be so you can just TAP the space bar to jump and the longer you hold it the higher you jump until of course you fall back down like always, that way you can make smaller jumps basically. Linear velocity can do that but the problem is that it takes way too much to fall down and I can't seem to speed any much of the physics up, it's really slow.
The way you describe is good.

You apply a velocity as long as the user holds a key. This turns the character into a rocket (constantly firing the engine). 

Keyboard sensor -&gt; AND/OR -&gt; Motion Actuator [LinV (0,0,1)]


Another way is to apply a force. The advantage is that it adds to the current velocity rather than replacing it. 

Keyboard sensor -&gt; AND/OR -&gt; Motion Actuator [Force (0,0,1)]


Hint:
Regarding slow falling - Are you aware that the default cube has a size of 2x2x2meters? If you box-modeled your character from that it might be a giant of 10+meters. It will surely fall slower as it travels a large distance.