Fluid Mechanics – Density and Buoyancy Problems
- A block of lead has dimensions of 4.50 cm by 5.20 cm by 6.00 cm. The block weighs 1587 g.
- From this information, calculate the density of lead in g/cm3.
- What is the density of lead in SI units? (kg/m3)
- 28.5 g of iron pellets are added to a graduated cylinder containing 45.50 mL of water. The water level rises to the 49.10 mL mark.
- From this information, calculate the density of iron in g/cm3? (Note: 1 mL = 1 cm3)
- What is the density of iron in SI units?
- A 100-cm3 block of lead that weighs 11 N is carefully submerged in water. (Density of water is 1g/mL or 1000 kg/ m3.)
- What volume of water does the lead displace?
- How much does that volume of water weigh in Newtons?
- What is the buoyant force on the lead?
- What is the apparent weight of the lead in water?
- Will the lead block float or sink in the water? How do you know – give two reasons?
- The same 100-cm3 lead block is carefully submerged in a container of mercury. One cm3 of mercury weighs 0.13 N.
- What volume of mercury is displaced?
- How much does that volume of mercury weigh?
- What is the buoyant force on the lead?
- What is the apparent weight of the lead? (Be careful here.)
- Will the lead block sink or float in the mercury? How do you know (give two reasons)?
- According to problems 3 and 4, does an object’s density have anything to do with whether or not it will float in a particular liquid? Justify your answer using the term buoyant force.
- A person has a mass of 80kg at sea level. She jumps into the swimming pool and her weight changes to 500 Newtons.
- What is her weight on Earth?
- What is her apparent weight in water?
- What is the buoyant force of the water acting on her?
- What was the weight of the water that was displaced when she jumped in the pool?
- What was the volume of water that was displaced when she jumped in?
- A piece of metal weighs 40N in water, 55 N in air, and 35 N in an unknown liquid. Find the densities of the following? (density of air = 1.29 kg/m3)
- The metal
- The unknown liquid
8. A beach ball has a volume of 0.75m3 and a mass of 0.15 kg. What mass can the beach ball support before sinking?
9. In lab you measure the following set of information:
a. Mass of a flat sheet of metal =251.3g
When placed in a full displacement tank of water, the flat sheet of metal sinks and displaces water into a beaker.
The mass of the empty beaker = 135.5g
The mass of the beaker containing the displaced water from the flat sheet of metal sinking = 361g
Determine the density of the flat sheet of metal.
9) With help from guided questions: In lab you measure the following set of information:
a) Mass of a flat sheet of metal =251.3g
When placed in a full displacement tank of water, the flat sheet of metal sinks and displaces water into a beaker.
The mass of the empty beaker = 135.5g
The mass of the beaker containing the displaced water from the flat sheet of metal sinking = 361g
Determine the density of the flat sheet of metal.
What is the weight of the object (Fg)?
What is the mass of the displaced fluid?
What is the weight of the displaced fluid (FF)?
What is the buoyant force acting on the metal (FB)?
What is the density of the metal (use equation for sinking objects)?
b. After shaping the same piece of metal into the shape of a bowl, the metal is placed into a full displacement tank of water and floats. Using the same dry beaker as before, the mass of the beaker and the displaced fluid is 541.8g. The boat is loaded with paper clips and can hold 140 paper clips of mass 1.5g each before it sinks? What is the density of the metal boat?
b. With help through guided questions: After shaping the same piece of metal into the shape of a bowl, the metal is placed into a full displacement tank of water and floats. Using the same dry beaker as before, the mass of the beaker and the displaced fluid is 541.8g. The boat is loaded with paper clips and can hold 140 paper clips of mass 1.5g each before it sinks? What is the density of the metal boat?
What is the weight of the boat (Fg)?
What is the mass of the displaced fluid?
What is the weight of the displaced fluid (FF)?
What is the buoyant force acting on the metal (FB)?
What is the approximate density of the boat just before it sinks in water?
What is the total mass of paper clips that is held by the boat?
What is the total mass of the boat and the paper clips?
Using the density immediately before it sinks calculate the volume of the boat?
Use the mass of the metal and this new volume to calculate the density of the boat.