# Are We Able To Feel The Ship Moving When We Are Onboard It?

Ships typically carry two things: cargo and people. But how do they do this safely, without everything and everyone falling over as soon as they move? This question requires us to consider the principles of physics.

Newton’s first law of motion

According to Newton’s first law of motion, an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless an unbalanced force is applied. In other words, objects tend to keep doing what they are doing.

This principle may initially seem counterintuitive: don’t objects eventually slow down or stop moving independently? The answer is no—an object stays in motion until forces like gravity or friction act on it. This is also known as the law of inertia, where objects experience resistance to change.

Relative velocity

All motion is relative—consider, for example, how you can’t feel the Earth spinning, although it is constantly revolving around the sun. You do not register the movement because you, too, are spinning with the Earth at a constant speed.

This phenomenon is also commonly experienced during car rides. A car moves with a certain velocity, which refers to its speed and the direction it travels. As you move with the car, the relative velocity between you and the vehicle is 0. This is also why your fellow passengers appear stationary while the trees and buildings outside seem to be moving backwards. There is no relative velocity between you and the other passengers, but the trees outside move at a different relative velocity with respect to everyone in the car.

However, you can feel movement when the speed of the car changes or when the car drifts.

Following the logic of the law of inertia, your speed changes along with the car’s: pressing on the brakes or the accelerator causes there to be an unbalanced force that disrupts movement. As you are inside the car, your speed changes along with the vehicle—but this does not happen instantly, so there will be a short period of mismatch, where the relative velocity between you and the car is not 0.

Therefore, if the car picks up speed, you will experience a tendency to resist acceleration, which manifests in you leaning backwards because your body at rest tends to stay at rest. Conversely, if the car suddenly stops, you will likely slide forward as you continue in motion—hence the importance of wearing the seatbelt.

What does this mean?

So, would you feel the ship moving while you’re onboard? There is no clear-cut answer to this question. Theoretically, if the ship is moving at a constant speed towards the same direction, you should not be able to feel its movement.

However, this is unlikely to hold in real life. With turbulent waters and unpredictable weather, the ship is unlikely to move with a constant velocity; hence, you can feel some of its movements.

Conclusion

By studying the physics behind movement and learning about the law of inertia and relative velocity, you can better understand how vehicles of all kinds work. If you are keen on learning more about physics principles in other everyday activities, engage a trusted provider for JC Physics Tuition in Singapore. Contact us to find out more!