Ship Opposing Force
1. **State the problem:** A ship initially travels at 18 km/h. After stopping its engines, it drifts 0.6 km and its speed reduces uniformly to 14 km/h. The ship's mass is 2000 t (which is 2,000,000 kg). We are asked to find the force opposing the motion of the ship.
2. **Convert units:** Speeds are given in km/h, convert to m/s for consistent SI units:
$$18\text{ km/h} = \frac{18 \times 1000}{3600} = 5 \text{ m/s}$$
$$14\text{ km/h} = \frac{14 \times 1000}{3600} = \frac{14000}{3600} \approx 3.8889 \text{ m/s}$$
Distance drifted:
$$0.6 \text{ km} = 600 \text{ m}$$
Mass:
$$2000 \text{ t} = 2000 \times 1000 = 2,000,000 \text{ kg}$$
3. **Calculate acceleration:** Since the speed reduces uniformly,
we use kinematics equation:
$$v^2 = u^2 + 2as$$
where
$u = 5 \text{ m/s}$ (initial speed),
$v = 3.8889 \text{ m/s}$ (final speed),
$s = 600 \text{ m}$ (distance),
$a$ is acceleration (deceleration here).
Plug in values:
$$3.8889^2 = 5^2 + 2a(600)$$
$$15.123 = 25 + 1200a$$
Solve for $a$:
$$1200a = 15.123 - 25 = -9.877$$
$$a = \frac{-9.877}{1200} = -0.00823 \text{ m/s}^2$$
(The negative sign indicates deceleration.)
4. **Calculate opposing force:** Using Newton’s second law,
$$F = ma$$
$$F = 2,000,000 \times (-0.00823) = -16460 \text{ N}$$
The negative sign indicates the force direction opposes the motion.
**Final answer:** The force opposing the motion of the ship is approximately $$1.65 \times 10^4 \text{ N}$$ acting opposite to the direction of travel.