Question

Which of the four cars had the least net force applied to it when it was launched down the ramp

Answer 1

The least net force applied : Car 3(12 N)

Further explanation  

Newton's 2nd law explains that the acceleration produced by the resultant force on an object is proportional and in line with the resultant force and inversely proportional to the mass of the object  

∑F = m. a  

Car 1 ⇒m=0.5 kg, a=36 m/s²

$\tt \sum F=0.5\times 36=18~N$

Car 2⇒m=0.8 kg, a=50 m/s²

$\tt \sum F=0.8\times 50=40~N$

Car 3⇒m=0.6, a=20 m/s²

$\tt \sum F=0.6\times 20=12~N$

Car 4⇒m=1, a=19~m/s²

$\tt \sum=1\times 19=19~N$