#### Answer

The projectile requires 0.041 s to reach that speed.

#### Work Step by Step

1. Calculate the acceleration of the projectile, using the net force and the mass:
$F = m\times a$
$4.9 \times 10^5N = 5.0kg \times a$
Divide both sides by $5.0kg$.
$\frac{4.9 \times 10^5N}{5.0kg} = a$
$9.8 \times 10^4$ $m/s^2 = a$
2. Find the time that is required to get $4.0 \times 10^3$ $m/s$:
$V = V_0 + at$
- Since the projectile starts with no speed (rest), $V_0 = 0 m/s$
$V = at$
$4.0 \times 10^3 m/s = 9.8 \times 10^4 m/s^2 \times t$
$\frac{4.0 \times 10^3m/s}{9.8 \times 10^4m/s^2} = t$
$t = 0.041$ $s$