vo = initial velocity = 11 cm/s
vf= final velocity = ?
a = acceleration = ?
t= time = 2.45 s
Δx = diplacement = xf -xi = -5 - 2.85 = -7.85 cm
Apply:
Δx = vot + 1/2 a t^2
-7.85 = 11 (2.45) + 1/2 (a) (2.45)^2
Solve for a:
-7.85 = 26.95 + 3 a
-7.85 - 26.95 = 3a
-34.8 / 3 = a
a = -11.6 cm/s^2