Answer:
4 seconds
Explanation:
Start with this observation: the distance traveled by car A, plus the distance traveled by car B, plus the original 15 meter gap, equals the 55 meter separation at time t.
dA + dB + 15 = 55
You're given the equation for distance traveled at constant acceleration when the initial velocity is 0:
d = 0.5at²
Given that the acceleration of car A is 2 m/s² and the acceleration of car B is 3 m/s², all you have to do is plug in the expressions and variables and solve for t.
0.5 (2) t² + 0.5 (3) t² + 15 = 55
t² + 1.5 t² = 40
2.5 t² = 40
t² = 16
t = 4
