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 ?
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Newton’s first law states that, unless influenced by something external, an object does not change the way it is moving. Something that is still remains still, and something that is moving remains moving.
If an object does change the way it is moving (i.e. if it accelerates), then there must be an external influence on it. We refer to influences that change an object’s motion as “forces”, and the amount of force acting on an object we *define* to be equal to its mass times the rate at which its motion changes*. This is Newton’s second law.
So, yes. If an object moves at constant speed, that means either A) there is no force acting on it or B) there are forces acting on it, but their combined effect is the same as if there were no forces acting. In either case, we would say that the net force on the object is zero.
*technically, force is defined as the rate of change of an object’s momentum, which is only equal to ma for objects with unchanging mass.
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