A car is going 3 m/s, then it speeds up for 4 seconds. If it has an acceleration of 5m/s^2, find its final velocity. Which equation can you use?

A Δx = vi*t + (½) at^2

B vf = vi + a*t

C Δx = (½) (vf + vi) * t

D vf^2 = vi^2 + 2aΔX

Well, since the question GIVES you the initial velocity, the acceleration, and the time, and ASKS for the final velocity, you'd be smart to find an equation that USES the initial velocity, the acceleration, and the time, and FINDS the final velocity.

Have a look at equation B ... vf = vi + a*t. That's pretty durn close!

vf = (initial velocity) + (acceleration) * (time)

vf = (3 m/s) + (5 m/s²) * (4 sec)

vf = (3 m/s) + (20 m/s)

vf = 23 m/s