For the body to remain stationary on the floor of the car, the pseudo force acting on the body must be balanced by the static frictional force. Thus, $ma \le \mu N$, where $N = mg$. Therefore, $ma \le \mu mg$, which simplifies to $a \le \mu g$. Given $\mu = 0.15$ and $g = 10 \text{ m s}^{-2}$, the maximum acceleration is $a = 0.15 \times 10 = 1.5 \text{ m s}^{-2}$.