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The answer depends on what information you have about the object.
If you know the object's mass "m" and that it is on the surface of the Earth, the object's weight is given by multiplying "m" by "g" (~9.81 m/s^2) which is the gravitational acceleration on Earth's surface. Thus, the weight would be given by
w = m*g.
If you know the object's mass "m" and that the object is near Earth, at a distance of "r" from the Earth's surface, where "r" is greater than the Earth's radius "R", then the weight of the object is given by:
w = G*m*M/r^2
where "G" is the universal gravity constant (~6.673 * 10^(-11) m^3 kg^-1 s^-2) and "M" is the mass of the Earth (~5.974 * 10^24 kg).
If you know the object's density "d" and volume "v" you can calculate its mass as m = d * v, and then multiply by either "g" or "GM/r^2" as appropriate from the above.
If you know the object is held by a spring with a spring constant "k" and the spring is extended by a distance "x" the weight of the object is causing the spring's extension, and since the spring force is given by k * x, and the weight causes the spring to be at equilibrium at that point, the weight of the object is given by:
w = k * x
In all the above, be careful to use SI units (e.g. kg, m, s, etc.) and you will find the answer is N (Newtons).
If you know the object's mass "m" and that it is on the surface of the Earth, the object's weight is given by multiplying "m" by "g" (~9.81 m/s^2) which is the gravitational acceleration on Earth's surface. Thus, the weight would be given by
w = m*g.
If you know the object's mass "m" and that the object is near Earth, at a distance of "r" from the Earth's surface, where "r" is greater than the Earth's radius "R", then the weight of the object is given by:
w = G*m*M/r^2
where "G" is the universal gravity constant (~6.673 * 10^(-11) m^3 kg^-1 s^-2) and "M" is the mass of the Earth (~5.974 * 10^24 kg).
If you know the object's density "d" and volume "v" you can calculate its mass as m = d * v, and then multiply by either "g" or "GM/r^2" as appropriate from the above.
If you know the object is held by a spring with a spring constant "k" and the spring is extended by a distance "x" the weight of the object is causing the spring's extension, and since the spring force is given by k * x, and the weight causes the spring to be at equilibrium at that point, the weight of the object is given by:
w = k * x
In all the above, be careful to use SI units (e.g. kg, m, s, etc.) and you will find the answer is N (Newtons).
source(s):
Studying and later teaching college physics.
Studying and later teaching college physics.
voted helpful: chazzyfen
'Weight' is defined as the pull of gravity on an object. You weigh an object on a spring scale calibrated in Newtons or Pounds Weight.
'Mass' is the amount of matter or 'stuff' in an object. You measure mass with a balance (teeter totter), using known masses on the other side of the balance to compare. When the balance is level, the earth is pulling on both masses equally. At that point, you know the masses are equal.
Incidentally, mass never changes, whereas weight can change depending on location. e.g. your mass on the Moon will be the same, as you have the same amount of matter in you. Your weight will be less (about one sixth) because the Moon's gravitational pull is much less.
'Mass' is the amount of matter or 'stuff' in an object. You measure mass with a balance (teeter totter), using known masses on the other side of the balance to compare. When the balance is level, the earth is pulling on both masses equally. At that point, you know the masses are equal.
Incidentally, mass never changes, whereas weight can change depending on location. e.g. your mass on the Moon will be the same, as you have the same amount of matter in you. Your weight will be less (about one sixth) because the Moon's gravitational pull is much less.
source(s):
Thirty years of teaching Physics :)
Thirty years of teaching Physics :)
We can calculate the weight of an object using the formula, F=mg (Weight=Mass x Acceleration due to gravity), where 'g' is approximately equal to 9.8m/s for earth.
tags: physics
The weight of an object depends on its mass and the gravitational field strength:
weight = mass x gravitational field strength
The units for these quantities are as follows:
Weight is measured in newtons (N).
Mass is measured in kilograms (kg).
Gravitational field strength is measured in newtons per kilogram (N/kg).
The gravitational field strength depends on the force of gravity. On Earth it is 10 N/kg, but it varies depending on planet size.
weight = mass x gravitational field strength
The units for these quantities are as follows:
Weight is measured in newtons (N).
Mass is measured in kilograms (kg).
Gravitational field strength is measured in newtons per kilogram (N/kg).
The gravitational field strength depends on the force of gravity. On Earth it is 10 N/kg, but it varies depending on planet size.
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