Answer
The ratio of $F_{T1}$ to $F_{T2}$ is 2.
Work Step by Step
For acceleration a, $F_{T1}$ causes the system of Car 1 + Car 2 to accelerate. Therefore $F_{T1} = 2ma$ , where m is the mass of each car.
For acceleration a, $F_{T2}$ causes the system of Car 2 to accelerate. Therefore $F_{T2} = ma$ , where m is the mass of Car 2.
$F_{T1} = 2ma$
$F_{T2} = ma$
$\frac{F_{T1}}{F_{T2}} = \frac{2ma}{ma}$
$\frac{F_{T1}}{F_{T2}} = 2$
The ratio of $F_{T1}$ to $F_{T2}$ is 2.
