# PHYSICS

9. An ebony log with volume 15.0 ft3 is submerged in water. What is the buoyant force on it (in lb)? (Enter the magnitude.)

lb=

10. An empty storage tank has a volume of 9,490 ft3. What is the buoyant force exerted on it by the air? (Assume the air is at 0°C and 1 atm.)

lb=

11. A modern-day zeppelin holds 9,770 m3 of helium. Compute its maximum payload at sea level. (Assume the helium and air to be at 0°C and 1 atm.)

N=

12. A boat (with a flat bottom) and its cargo weigh 6,400 N. The area of the boat’s bottom is 5 m2. How far below the surface of the water is the boat’s bottom when it is floating in water?

m=

13. A scale reads 378 N when a piece of iron is hanging from it. What does it read (in N) when it is lowered so that the iron is submerged in water?

N=

14. A dentist’s chair with a person in it weighs 2000 N. The output plunger of a hydraulic system starts to lift the chair when the dental assistant’s foot exerts a force of 44 N on the input piston. Neglecting any difference in the heights of the piston and the plunger, what is the ratio of the area of the plunger to the area of the piston?

*A*plunger/*A*piston =

15. The wing of an airplane has an average cross-sectional area of 13 m2 and experiences a lift force of 91,000 N. What is the average difference in the air pressure between the top and bottom of the wing?

N/m2=

16. Air flows through a heating duct with a square cross-section with 9-inch sides at a speed of 4.1 ft/s. Just before reaching an outlet in the floor of a room, the duct widens to assume a square cross-section with sides equal to 15 inches. Compute the speed of the air flowing into the room (in ft/s), assuming that we can treat the air as an incompressible fluid.

ft/s=

17. A metal bowl with a weight of 1.45 N is placed in a larger kitchen container filled with olive oil. How much olive oil must the bowl displace in order to float? For reference, the mass density of olive oil is about 910 g/liter and its weight density is about 8.92 N/liter. Please give your answer in liters.