Hydrostatic – Hydrostatic Pressure – EN
Hydrostatics
Hydrostatic Pressure
Exercises with ENEM characteristics
01-(UFMG-MG)
A water tank consists of two interconnected cylindrical parts, as shown in the figure.
The cross-sectional area of the lower cylinder is larger than that of the upper cylinder.
Initially, this reservoir is empty. At a certain point, it begins to fill with water, maintaining a constant flow.
Select the alternative whose graph BEST represents the pressure at the bottom of the reservoir as a function of time, from the moment it starts to fill until the moment it starts to overflow.
02-(PUC-MG)
The figure shows two water tanks, open to the air, connected by a pipe with a check valve. The tank on the left is full. When the valve is opened, the tank on the right
starts filling until the water level in both boxes is the same.
It is CORRECT to state:
a) At the end of the process, the pressure at the bottom of the box on the left will be lower than at the beginning.
b) During the process, the water flow speed is constant.
c) At the end of the process, the pressure at the bottom of the box on the right will be greater than the pressure at the bottom of the box on the left.
d) During the process, the water flow speed increases.
03-(FUVEST-SP)
The human body can be subjected, without harmful consequences, to a pressure of up to 4.105 N /m2 and a pressure change rate of up to 104 N /m2 per second.
The maximum depth for a diver and the maximum recommended vertical movement speed can be, respectively:
Data: density of water = 1.0.103 kg /m3 — local atmospheric pressure – 1.0.105 N /m2 — acceleration of gravity = g = 10m/ s2
a) h=20 m and V=2 m/s
b) h=30 m and V=3 m/s
c) h=40 m and V=4 m/s
d) h=30 m and V=1 m/s
e) d) h=25 m and V=2 m/s
04-(UFRJ-RJ)
Two fugitives must cross a lake without being noticed. To do so, they capsize a small boat, which sinks with the help of additional weights. The capsized boat retains a certain amount of air trapped inside it, as shown in the figure.
At the instant depicted, both the boat and the fugitives are at rest and the water is in hydrostatic equilibrium. Consider the density of the lake water to be 1.00.103 kg /m3 and the acceleration of gravity to be 10.0 m/ s2 .
Using the data shown in the figure, calculate the difference between the pressure of the air trapped by the boat and the pressure of the atmospheric air.
a) 5.0.10 3 N/m 2
b) 8.5.10 3 N/m 2
c) 15.2.10 4 N/m 2
d) 9.0.105 N / m2
e) 5.0.106 N / m2
05-(UEL-PR)
The siphon is normally used in sinks and toilets to prevent the passage of gases and small animals inside the house.
In addition to the siphon, a “breather” is used, that is, an opening, connected to the external atmosphere through a pipe, which:
a) Keeps pressures equal on both sides of the siphons, helping to keep water levels balanced.
b) It serves to maintain ventilation in the discharge system.
c) It is used to drain excess water when flushing the toilet.
d) It is used to remove the very loud sound of discharges.
e) Increases the fluidity of water, helping it to flow.
06-(UDESC-SC)
A certain amount of water is placed in a U-shaped tube, open at the ends. In one of the branches of the tube, a liquid with a greater density than water is added and the two do not mix.
Select the alternative that correctly represents the position of the two liquids in the tube after equilibrium.
07-(PUC-RS)
A container open at the top contains glycerin up to a height of 1.00 m and, above it, more
10.0 cm of water, as shown in the figure. Consider the specific mass of water to be 1.00 g/cm 3 and of glycerin to be 1.30 g/cm 3 . Use the acceleration of gravity to be 10.0 m/s 2 and the atmospheric pressure to be 1.01.10 5 Pa. In this case, the pressure, in pascals, at the water-glycerin interface and at the bottom of the container is, respectively, _________ and _________.
a) 1.02.10 5 1.34.10 5
b) 1.21.10 5 1.34.10 5
c) 1.02.10 5 1.25.10 5
d) 1.01.10 5 1.21.10 5
e) 1.02.10 5 1.15.10 5
08-(UECE-CE)
In the elevator shown in the following figure, the car in the left cylinder at position E has a mass of 900 kg, and the cross-sectional area of the cylinder is 2500 cm 2 . Assume the mass of the piston is negligible and the acceleration of gravity is 10 m/s 2 . The cross-sectional area of the cylinder at position D is 25 cm 2 , and the piston has negligible mass.
If the elevator is filled with oil of density 900 kg/m3 , the minimum force F, in Newtons, required to keep the system in equilibrium will be
09-(UFF-RJ)
A siphon is an instrument used to remove water from hard-to-reach places. As shown in the
figure below, its operation is based on the fact that, when the tube connecting containers A and B is full, there is a difference in hydrostatic pressure between points P and Q, which causes a flow of water from A to B.
This pressure difference depends on the following characteristic of our planet:
a) atmospheric pressure.
b) local acceleration of gravity.
c) surface temperature.
d) density of the atmosphere.
e) speed of rotation of the planet.
10-(UNICAMP-SP) TEXT FOR THE NEXT QUESTION:
The oil spill in the Gulf of Mexico in April 2010 was considered the worst in US history. The spill caused a large oil slick to appear on the ocean surface, threatening the region’s fauna and flora. It is estimated that the spill
was in the order of 800 million liters of oil in about 100 days.
When an underwater oil reserve is hit by a drilling rig, the oil tends to flow upward in the pipeline.
as a consequence of the pressure difference, ΔP, between the reservoir and the surface. For an oil reservoir that is at a depth of 2000 m and given g = 10 m/s 2 , the smallest value of ΔP for the oil of density ρ = 0.90 g/cm 3 to form a column that reaches the surface is
a) 1.8.10 2 Pa.
b) 1.8.10 7 Pa.
c) 2.2.10 5 Pa.
d) 2.2.10 2 Pa.