Atugboat pulls two barges down the river. the barge connected to the tugboat, carrying coal, has an inertia of 2.5 × 105 kg, and the other barge, carrying pig iron, has an inertia of 3.5 × 105 kg. the resistive force between the coal barge and the water is 8.0 × 103 n, and the resistive force between the pig iron barge and the water is 1.0 × 104 n . the common acceleration of all three boats is 0.40 m/s2. even though the ropes are huge, the gravitational force exerted on them is much smaller than the pulling forces.