The public is not yet able to purchase hydrogen fuel cell powered cars because engineers have to determine

This would more a practical feedback than scientific.

Explanation: Despite of the protocols and processes scientists need to develop in order to stablish a new source of energy or daily life option, logistic issues are one of the most important things on the "to do list".

Would it be very expensive to acquire this kind of fuel? Is it efficient? Is it dangerous to human life or the environment? What about the negative reactions this brand new fuel could have in society?.

the force on the thing and the distance the force moves the thing