http://s7.postimage.org/okqoitawr/phy.jpg Three objects of identical mass attach
ID: 1893945 • Letter: H
Question
http://s7.postimage.org/okqoitawr/phy.jpg
Three objects of identical mass attached to strings are suspended in a large tank of liquid, as shown above.
(a) Must all three strings have the same tension?
____ Yes ____ No
Justify your answer.
Object A has a volume of 1.0 x 10-5 m3 and a density of 1300 kg/m3. The tension in the string to which
object A is attached is 0.0098 N.
(b) Calculate the buoyant force on object A.
(c) Calculate the density of the liquid.
(d) Some of the liquid is now drained from the tank until only half of the volume of object A is submerged. Would the tension in the string to which object A is attached increase, decrease, or remain the same?
____ Increase ____ Decrease ____ Remain the same
Justify your answer.
Explanation / Answer
(a) no all the strings will not have same tension because their weight is same so downward Mg will be same for all the three but since their volume is not same so upward buoyant force is different for different object and so the overall tension on the string. the bigger object will have lesser tension.
(b) mass of object A = 1.0 x 10-5 m3 X 1300 kg/m3 =0.013 kg
weight of A will be 0.013 kg X9.8m/s2 = 0.1274 N
since the tension in the string is 0.0098 N
buoyant force will be 0.1274-0.0098 = 0.1176 N
(C) density of the liquid will be calculated as follow
the buoyant force we calculated in (b) is the weight of the displaced water
mass of displaced water will be 0.1176/9.8 m/s2 = 0.012kg
and volume of water displaced is equal to the volume of solid object wich is equal to 1.0 x 10-5 m3
density of water is 0.012kg / 1.0 x 10-5 m3 = 1200 Kg/m3
(d) when few water is drained so that only half of A is drained then tension in the string of A will increase because downward weight is remaining same and upward buoyant force will decrease (because of less water displacement )so the tension will increase.
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