A car enters the freeway with a speed of 7.2 m/s south and accelerates uniformly for 4.2 km in 4.0 min. How fast (in m/s) is the car moving after this time?

Question

I only need the formula.
My teacher gave us a list but did not tell the class which equation is for which.
Help please.

Answer 1

x = Xi + Vi t + (1/2) a t^2

4200 = 0 + 7.2 t + (1/2) a t^2
but t = 4 * 60 = 240 seconds
so

4200 = 7.2(240) + .5 a (240)^2
solve for a

then
v = Vi + a t
v = 7.2 + a (240)

Answer 2

Thank you so much! You didn't have to solve it for me, I only needed the formula, but thanks a lot!^^