How many giant balloons

It depends on the specific circumstances such as the size, weight, and momentum of the "giant steel draft" (which I assume refers to a large moving object or structure made of steel) and the power and capabilities of the four cars involved.

If the steel draft is a massive object with significant inertia and the four cars are typical consumer vehicles, it’s unlikely that they could stop it, especially if it’s moving at speed. Steel is dense and heavy, and halting its motion would require a force equal to or greater than the momentum it has. The cars would need sufficient traction, weight distribution, and power to counteract the motion of the steel object.

If the cars are specifically designed for towing or stopping large objects (e.g., heavy-duty trucks or specialized vehicles), and they coordinate properly, they might be able to slow it down or even stop it under the right conditions. However, without specific details about the size and speed of the steel draft, and the type of cars, it’s hard to say definitively.

Physics-wise, the total force needed to stop a moving object is determined by the mass and velocity of the object (F = ma), so stopping a massive steel structure would require considerable braking force.