Answer
$a = 0$
$v = 4~m/s$
Work Step by Step
We can find the acceleration from t = 0 to t = 3 s:
$a = \frac{F}{m}$
$a = \frac{4.0~N}{2.0~kg}$
$a = 2.0~m/s^2$
We can find the acceleration from t = 3 s to t = 5 s:
$a = \frac{F}{m}$
$a = \frac{-2.0~N}{2.0~kg}$
$a = -1.0~m/s^2$
We can find the acceleration from t = 5 s to t = 7 s:
$a = \frac{F}{m}$
$a = \frac{0}{2.0~kg}$
$a = 0$
At t = 6 s:
Since the force on the object is zero, the acceleration is also zero.
We can find the velocity at t = 3 s:
$v = a~t = (2.0~m/s^2)(3~s) = 6~m/s$
We can find the velocity at t = 5 s. We can let $v_0=6~m/s$ for this part of the question.
$v = v_0+ a~t$
$v = (6~m/s)+ (-1.0~m/s^2)(2~s) = 4~m/s$
Since the object does not accelerate after t = 5 s, the velocity at t = 6 s is $4~m/s$.
