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Chap 13 Solutions copy

Chap 13 Solutions copy - 13 FLUIDS Q13.1 Reason Density...

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13-1 F LUIDS 13 Q13.1. Reason: Density does not depend on the volume. That is, 1 g of mercury would have the same density as 1000 g of mercury, and 1 g of water would have the same density as 1000 g of water. Table 13.1 shows the density of mercury to be 13,600 kg/m 3 and that of water to be only 1000 kg/m 3 . The density of 1 g of mercury is 13.6 times as much as the density of 1000 g of water. Assess: It is important to get used to the idea that density is a ratio of mass to volume, so different samples of the same substance would have the same density. Q13.2. Reason: Equations 13.1 and 13.2 apply. (a) Using Equation 13.1, ! = m V = 3 kg 1 " 10 # 3 m 3 = 3 " 10 3 kg/m 3 (b) The mass becomes m = ! V = (3 " 10 3 kg/m 3 )(2 " 10 # 3 m 3 ) = 6 kg. (c) Density only depends on the type of material. The density will not change when the volume is doubled. Using the mass calculated in part (b) , we can explicitly calculate the density as ! = m / V = 6 kg/2 " 10 # 3 m 3 = 3 ! 10 3 kg/m 3 . This is the same as the original density, as expected. Assess: Density is an intrinsic property of a material. It does not change depending on the actual volume or mass of material. Q13.3. Reason: If the chunk is heavy (dense) enough to sink in water you would put the chunk into a known volume of water in a graduated cylinder and note the rise; this would give the volume of the chunk. A simple measurement of the chunk’s mass on a pan balance would then allow you to use ! = m / V . Assess: If the chunk floats in water then you would have to find a way to submerse it to find the volume. Q13.4. Reason: Density is given by Equation 13.1. (a) The size and shape of the two objects is the same, so the volume of the two objects is the same. The second object has twice the mass as the first so its density is ! 2 = 2 m / V = 2 ! 1 . The second object has twice the density of the first. (b) The third object has a size in all three dimensions twice that of the first object. Its volume is eight times that of the first object. Since its mass is the same, the density of the third object is ! 3 = m /8 V = 1 8 ! 1 . The density of the third object is one eighth that of the first. Assess: To make the volume increase in part (b) more concrete, consider increasing the length of each side of a cube by a factor of two. The volume increases by a factor of 2 ! 2 ! 2 = 8. Q13.5. Reason: It all has to do with pressure increasing with depth, which is a result of the gravitational force. If, when receiving a transfusion, the bag were held below your body the blood would not flow up into your body, and if, when donating blood, the bag were held above your body, no blood would flow up into it. The blood wants to flow down. Assess: It is kind of neat to notice things like this and think physics thoughts, even while getting a transfusion or donating blood!
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13-2 Chapter 13 Q13.6. Reason: The pressure at a depth of 10 m is p = p 0 + ! gh = 1.013 " 10 5 Pa + (1000 kg/m 3 )(9.80 m/s 2 )(10 m) = 2 " 10 5 Pa This is almost twice atmospheric pressure. It will be difficult for Tom to inhale.
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