Answer:
6 m/s
Explanation:
At constant acceleration, the final velocity is equal to the initial velocity plus the product of time and acceleration:
v = at + v₀
We know that at t=2, v=12. And at t=4, v=18.
12 = 2a + v₀
18 = 4a + v₀
We can solve the system of equations for v₀. If we double the first equation:
24 = 4a + 2v₀
And subtract the second:
24-18 = 4a-4a + 2v₀ - v₀
6 = v₀
The initial velocity is 6 m/s.