We can use the formula for resistance to motion:
R = (m(vf^2 - vi^2))/(2d)
where R is the resistance to motion, m is the mass of the ship (10 000 tonnes = 10,000,000 kg), vf is the final velocity (2 m/s), vi is the initial velocity (3 m/s), and d is the distance over which the ship slowed down (40 m).
Plugging in the values, we get:
R = (10,000,000((2^2) - (3^2)))/(2(40))
R = (10,000,000(-5))/80
R = -625,000 N
The negative sign indicates that the resistance to motion is acting in the opposite direction to the ship's motion. Therefore, the average resistance to motion of the ship when slowing down is 625,000 N.