Which one of the following statements is incorrect?

$A$ truck starting from rest moves with an acceleration of $5 \, m/s^2$ for $1 \, s$ and then moves with constant velocity. The velocity $w.r.t$ ground $v/s$ time graph for the block in the truck is (Assume that the block does not fall off the truck and the coefficient of friction $\mu = 0.2$):

The curve between net force and time is shown. Initially,the particle is at rest. Which of the following best represents the resulting velocity-time graph of the particle?

$A$ $\sqrt{34}\,m$ long ladder weighing $10\,kg$ leans on a frictionless wall. Its feet rest on the floor $3\,m$ away from the wall as shown in the figure. If $F_{f}$ and $F_{w}$ are the reaction forces of the floor and the wall,then the ratio of $F_{w}/F_{f}$ will be:
(Use $g=10\,m/s^{2}$)

$A$ horizontal force $12 \, N$ pushes a block weighing $1/2 \, kg$ against a vertical wall. The coefficient of static friction between the wall and the block is $0.5$ and the coefficient of kinetic friction is $0.35$. Assuming that the block is not moving initially,which one of the following choices is correct? (Take $g = 10 \, m/s^2$)

$A$ vehicle without passengers is moving on a frictionless horizontal road with velocity $u$ and can be stopped in a distance $d$. Now,$40\%$ of its weight is added. If the retardation remains the same,what is the stopping distance at velocity $u$?