will a body weigh more in air or in vacuum when weighed with a spring balance? give a reason for your answer
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There are two things causing confusion here.
The first is the wording of the question. The body weighs what it weighs, which is (mg). The question should read:
"Will the spring balance show a higher reading when the body is in air or vacuum?"
The second thing is the way that we all call g "The acceleration due to gravity". We call it that because it happens to be the acceleration of a body in free-fall. Unfortunately it sometimes causes confusion by making people think about kinematics.
In this case, where the body is in static equilibrium, it would be better to call it by its other name, which is "gravitational field strength", and use its alternative units N/kg.
If you hang the body on the hook of the spring balance, it will cause the spring to extend until the spring force upwards is equal in magnitude but opposite in direction to the weight force downwards.
The net force acting on the body will then be zero and the pointer will indicate the weight on the scale.
If the body is in a vacuum, that accounts for all the forces acting on the body.
If the body is immersed in a fluid however, there will be an extra force contributing to the equilibrium. That is the upthrust (F) due to the weight of fluid displaced by the body.
In this case, the spring will only need to extend until the spring force is equal (mg -F) in order for the net force on the body to be zero and the object to be in static equilibrium. The scale reading will therefore be lower than that in vacuum.
Air has a low density compared to liquids, so the weight of air displaced, and hence the upthrust force, will probably not be large.
The first is the wording of the question. The body weighs what it weighs, which is (mg). The question should read:
"Will the spring balance show a higher reading when the body is in air or vacuum?"
The second thing is the way that we all call g "The acceleration due to gravity". We call it that because it happens to be the acceleration of a body in free-fall. Unfortunately it sometimes causes confusion by making people think about kinematics.
In this case, where the body is in static equilibrium, it would be better to call it by its other name, which is "gravitational field strength", and use its alternative units N/kg.
If you hang the body on the hook of the spring balance, it will cause the spring to extend until the spring force upwards is equal in magnitude but opposite in direction to the weight force downwards.
The net force acting on the body will then be zero and the pointer will indicate the weight on the scale.
If the body is in a vacuum, that accounts for all the forces acting on the body.
If the body is immersed in a fluid however, there will be an extra force contributing to the equilibrium. That is the upthrust (F) due to the weight of fluid displaced by the body.
In this case, the spring will only need to extend until the spring force is equal (mg -F) in order for the net force on the body to be zero and the object to be in static equilibrium. The scale reading will therefore be lower than that in vacuum.
Air has a low density compared to liquids, so the weight of air displaced, and hence the upthrust force, will probably not be large.
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the more will be in air. if you suppose that you are in space the vaccum is great then in air.
when a spaceship comes towards earth the more its weight is weighted.
when a spaceship comes towards earth the more its weight is weighted.
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