Why aren't hydrogen fuel cell cars currently available to the public?

What tightening torque should be used for a hexagonal head screw (not split-bolt) on a 250 kcmil conductor?

Which articulations allow for greatest range of motion?

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.