Review Questions on Archimedes 1. A block of gold and a block of wood both have the same volume. If they are both submerged in water, which has the higher buoyant force? 2. A 100-­‐cm3 block of lead that weighs 11 N is carefully submerged in water. 1 cm3 of water weighs 0.0098 N. a. What volume of water does the lead displace? b. How much does that volume of water weigh? c. What is the buoyant force on the lead? d. Will the lead block sink or float in the water? 3. The same 100-­‐cm3 lead block is carefully submerged in a container of mercury. One cm3 of mercury weighs 0.13 N. a. What volume of mercury is displaced? b. How much does that volume of mercury weigh? c. What is the buoyant force on the lead? Answer d. Will the lead block sink or float in the mercury? c. What is the buoyant force on the lead? Answer -13 N
d. Will the lead block sink or float in the mercury? Answer - float
4. According to problems 2 and 3, does an object’s density have anything to do with whether or not it will float
in a particular liquid? Justify your answer. Answer – if an object is denser than the fluid it is placed in it will
sink, if the
the fluideit
will float.
4. Bobject
ased oisn less
the tdense
able othan
f densities, xplain whether the object would float or sink in the following situations: 5. Based on
the table of densities, explain whether the object would float or sink in the following situations:
material
a.
b.
c.
d.
density (g/ cm3)
gasoline
0.7
gold
19.3
lead
11.3
mercury
13.6
molasses
1.37
Paraffin(wax)
0.87
platinum
21.4
a. A block of solid paraffin (wax) in molasses. A block of solid paraffin (wax) in molasses. Answer - floats
b. A bar of gold in mercury. A bar of gold in mercury. Answer - sink
c. A piece of platinum in gasoline. A piece of platinum in gasoline. Answer - sinks
block oin
f pgasoline.
araffin in Answer
gasoline. A blockd. ofAparaffin
-sink
More questions on fluids and pressure: 5. What causes pressure in fluids? 6. What is the mathematical relationship between force, pressure, and area? A
Name _______________________________ Date ________________ Period _______
Pressure and Buoyancy Test
7. Examine the illustration of an iceberg below and answer the questions that follow. Examine the illustration of an iceberg below and answer the questions that follow.
1. At what point (a, b, or c) is the water pressure greatest on the iceberg? 2. Why is there more pressure at this point than the others? 1. At what point (a, b, or c) is the water pressure greatest on the iceberg?
2. Why is there more pressure at this point than the others?
8. What creates more pressure, a 200N box with a base of 10m2 or a 300N box with a base of 30m2? Show your work! 9. You apply a force of 50 N to the plunger of a syringe with a radius of 1 cm. How much pressure is exerted on the plunger? 10. What force is applied if you put 220 kPa of pressure on a 50-­‐m2 surface? 11. What principle is at work in each of the following situations? (Bernouilli, Archimedes, Pascal) a) the propellers of a boat b) a hydraulic press c) an anchor dropped in the water d) a hydraulic brake system Answers: 1. If they are both submerged, they displace the same amount of fluid, therefore their buoyant force is the same. 2. 3. Answer – 100 cm3 4. Answer – 0.0098 x 100 = 0.98 N 5. Answer -­‐ 0.98 N 6. Answer -­‐sink 3. a. Answer – 100 cm3 b. Answer – 0.13 x 100 = 13 N c. Answer -­‐13 N d. Answer -­‐ float 4. a. Answer -­‐ floats b. Answer -­‐ sink c. Answer -­‐ sinks d. Answer -­‐sink 5. Pressure is created when particles are forced to collide with one another. 6. P = F/A 7. 1. C, 2. There is more pressure because there is a greater mass of water pushing down onto this point. (Fg is greater) 8. 200N/ 10m2 = 20 Pa, 300N/30m2 = 10 Pa; the box with a 10m2 base exerts more pressure. 9. Surface of the piston = π r2 Surface in m2 = π (0.01)2 = 0.000 314 m2 Surface in m2 50 N P = 0.000 314 m2 P = 159 235 Pa, or 159.24 kPa 10. First, I convert 220 kPa into pascals: 220 000 Pa P × A 220 000 Pa × 50 m2 11. = F = 11 000 000 N Bernoulli’s principle Pascal’s principle Archimedes’ principle Pascal’s principle