If a car moves consistently at 80 kmh and it weighs at 600kg, is it not generating any force? since you know, a=0, am I stupid or is Newton ?
In: 13
> If a car moves consistently at 80 kmh and it weighs at 600kg, is it not generating any force?
Correct.
When you’re in a car, you can’t feel it moving if the speed is constant. You can only feel it changing its velocity or direction.
Or perhaps a better example is a plane. You can feel forces during take off, landing, and turbulence, but do you feel anything when the plane is in constant motion? No it feels no different than when it’s sitting there on the runway.
This is a core principle of relativity–and not just special relativity, but Galilean Relativity, which Galileo worked out hundreds of years ago. He claimed that if you were below deck on a boat, and the sea was smooth, there is no experiment you can do that could determine if the boat is in motion or not. He was right–pretty clever for a guy who had never actually been on a boat.
And that was important, because one of the main arguments against his claim that the Earth revolved around the Sun was that surely if the Earth was moving we’d be able to feel it.
If you could feel force from just velocity, then you’d feel the force of Earth rotating at 460 metres per second right now. Instead, it feels like you’re sitting still.
Also, an important note: in physics, “acceleration” doesn’t just mean “getting faster”. Any change of velocity is acceleration–including slowing down or changing direction. Changing direction without changing speed is still acceleration, that’s why you feel a force when your car turns around a corner.
Latest Answers