Human.physicsBody.velocity = CGVectorMake(0, 0);

[Human.physicsBody applyImpulse:CGVectorMake(0, 40)];

else if ((firstBody.categoryBitMask & HumanCategory) != 0 &&
         (secondBody.categoryBitMask & BlockCategory) != 0)
{

}

//Please note that this point is in the scenes coordinate system
CGPoint thePointDirectlyBelowMyNode = ...;
[scene.physicWorld bodyAtPoint:thePointDirectlyBelowMyNode];