w= is by box on earthOrodruin said:
Because it does not exert a force on a spring scale that is not at rest under it.PeroK said:
He just grinned and shook my hand. "No", was all he said!kuruman said:Because it does not exert a force on a spring scale that is not at rest under it.
This.kuruman said:
Two equal and opposite forces on the same object that result in a stationary object remaining stationary are what I like to call a "second law pair". The net force is zero, so the acceleration is zero by ##F=ma##.kuruman said:
Also, this is simply wrong. Both W and B are forces from the Earth on the box (with the further subdivision into Earth surface/entire Earth given above). W is the gravitational force of the Earth on the box, not the gravitational force of the box on the Earth.hello478 said:
Others have explained why W and B are not a second law pair. There is also clue in the question: "forces of the same type". The type distinction being made here is gravitational forces versus contact forces.hello478 said:
That's another good way to put it. In everyday life, a bathroom scale "measures your weight". In the physics classroom it measures the normal force exerted on its top surface when the scale is at rest with respect to the center of the Earth.Orodruin said:
Or, slightly more precisely, the normal force exerted on its top surface when its base remains at rest with respect to the rotating frame in which the Earth is stationary.kuruman said:
No. W and B act on the same object so they can't be a third-law pair.hello478 said:
Newton's third law of motion states that for every action, there is an equal and opposite reaction. This means that if one object exerts a force on another object, the second object exerts a force of equal magnitude but in the opposite direction on the first object.
Weight is the force exerted by gravity on an object, and according to Newton's third law, the object also exerts an equal and opposite force on the Earth. This means that while we feel the force of gravity pulling us down, the Earth is also being pushed upward by the same amount of force.
Yes! When a person stands on a scale, their weight exerts a downward force on the scale due to gravity. In response, the scale exerts an equal upward force on the person. This is why the scale shows a reading of the person's weight, as it measures the force exerted against it.
Yes, weight can change with location due to variations in gravitational force. For instance, a person weighs less on the Moon than on Earth because the Moon's gravitational pull is weaker. However, regardless of where you are, the action-reaction pairs described by Newton's third law still hold true; the person still exerts a force on the Moon equal to their weight.
Understanding Newton's third law helps engineers and architects design structures that can effectively distribute weight. For example, when a load is placed on a beam, the beam must exert an equal and opposite force to support that load. This principle is crucial in ensuring that buildings and bridges can withstand the forces acting on them without collapsing.