platform upside down

hi,
I want to ask please about platform (for basic car) with 4 wheels and 2 dc motors - if I want to put something long on the platform how I can connect between motors power to this and to my platform?- I mean how to avoid too much power from motors that can cause the car to turn upside down(how long something can be on the platform), on other hand, how to calculate that my motors will move my platform -how much power I need?

Tank you/

yelenaa1:
I want to ask please about platform (for basic car) with 4 wheels and 2 dc motors - if I want to put something long on the platform how I can connect between motors power to this and to my platform?- I mean how to avoid too much power from motors that can cause the car to turn upside down(how long something can be on the platform), on other hand, how to calculate that my motors will move my platform -how much power I need?

How big is this platform? What will it carry?

How fast do you want it to travel?

How heavy will it be? Lots of numbers please, numbers are needed to calculate anything!