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If I place 1 kg of feathers on a balance will the balance read the same as if I placed 1 kg of lead?
Yes, if you place 1 kg of feathers and 1 kg of lead on a balance, the balance will read the same weight, which is 1 kg.
The reason for this is that weight is a measure of the force exerted on an object due to gravity, and this force is directly proportional to the mass of the object, regardless of the material it is made of.
The mass of an object is a measure of the amount of matter it contains, and this is what determines the weight of the object when placed in a gravitational field. The density of the material (feathers vs. lead) does not affect the weight, as long as the total mass is the same.
So in this case, 1 kg of feathers and 1 kg of lead will both exert the same downward force on the balance, resulting in the same weight reading of 1 kg.
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what if the balance and the objects were surrounded by air and not by vacuum?
Even if the balance and the objects (1 kg of feathers and 1 kg of lead) are surrounded by air and not by vacuum, the weight reading on the balance will still be the same for both objects.
The reason is that the buoyant force exerted by the air on the objects is negligible compared to the gravitational force acting on them.
The buoyant force is the upward force exerted by a fluid (in this case, air) on an object immersed in it. This force is proportional to the volume of the object and the density of the fluid.
However, the density of air is much lower than the density of the objects (feathers and lead). As a result, the buoyant force acting on the objects is very small compared to their weight.
Therefore, the presence of air around the balance and the objects does not affect the weight reading, which will still be 1 kg for both the feathers and the lead. The weight measurement is primarily determined by the gravitational force acting on the mass of the objects, not the buoyant force of the surrounding air.
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what is the buoyant force exerted on 1 kg of feathers and on 1 kg of lead in air?
Okay, let's calculate the buoyant force exerted on 1 kg of feathers and 1 kg of lead when they are surrounded by air.
The buoyant force (F_b) is given by the formula:
F_b = ρ_fluid * V_object * g
Where:
ρ_fluid is the density of the fluid (in this case, air)
V_object is the volume of the object
g is the acceleration due to gravity
For air at standard temperature and pressure, the density is approximately 1.225 kg/m^3.
For 1 kg of feathers:
Mass of feathers = 1 kg
Density of feathers ≈ 0.05 kg/m^3 (very low)
Volume of 1 kg of feathers = 1 kg / 0.05 kg/m^3 = 20 m^3
Buoyant force on 1 kg of feathers = 1.225 kg/m^3 * 20 m^3 * 9.8 m/s^2 = 239.9 N
For 1 kg of lead:
Mass of lead = 1 kg
Density of lead ≈ 11,340 kg/m^3
Volume of 1 kg of lead = 1 kg / 11,340 kg/m^3 = 0.000088 m^3
Buoyant force on 1 kg of lead = 1.225 kg/m^3 * 0.000088 m^3 * 9.8 m/s^2 = 0.0105 N
As you can see, the buoyant force on the 1 kg of feathers (239.9 N) is much greater than the buoyant force on the 1 kg of lead (0.0105 N). This is due to the large difference in their volumes.
However, these buoyant forces are still negligible compared to the gravitational force acting on the objects, which is 9.8 N for both 1 kg of feathers and 1 kg of lead. Therefore, the weight reading on the balance will still be the same for both objects.