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phy 121
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A ball of mass 400 grams is immersed in water. The ball is suspended in the water by a rubber band chain which exerts a tension force of 2.5 Newtons on the ball.
• What is the weight of the ball?
answer/question/discussion: ->->->->->->->->->->->-> :
The ball weighs its mass times the force of gravity:
0.4kg *9.8m/s^2 = 3.92N
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• What is the buoyant force on the ball?
answer/question/discussion: ->->->->->->->->->->->-> :
Here we either have to combine the force of the tension and the weight or subtract. The rubber band exerts a tension force of 2.5N on the mass, and the mass (with weight of 3.92N) exerts a force on the rubber band. This should make for a net force of 3.92-2.5N = 1.42N. Without the rubber band the ball would exert the total force of 3.52N, but a 2.5N force is being exerted on the ball, this is my reasoning for subtracting here which makes the most sense to me. I cannot recall our measurement as accurately as I wish, but 1 gram of mass displaces 1 cubic centimeter of water. Therefore a 400 gram mass displaces 400 cubic centimeters of water.
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• What therefore must be its volume?
answer/question/discussion: ->->->->->->->->->->->-> :
I don’t know how much water is in whatever we’re submerging the mass in, or how far it is submerged, but im sure I will find out shortly neither of those quantities are necessary to solve for the appropriate answer, nevertheless, the volume I do currently have is 400cm^3.
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The buoyant force is equal to the weight of the water displaced by the object.
The mass of 1 cm^3 of water is 1 gram. 1 liter is 1000 cm^3 and has a mass of 1 kilogram.
That's all the information you need to answer the question. I expect you can and will figure it out, but if not you're welcome to ask.
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• What is its density?
answer/question/discussion: ->->->->->->->->->->->-> :
density is mass / volume :
400g/400cm^3 = 1g/cm^3
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That would be the mass and volume of 400 cm^3 of water, but it's not the mass and volume of the object.
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*#&!
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Good start. Check my note and see if you can get the rest.
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