V.6. Summary - Pressure.

• V.6.1. Pressure.
• V.6.2. Worksheet - Fluid Statics.

V.6.1. Pressure.

📚 Summary

Characterization of pressure as physical parameter:

V.6.2. Worksheet - Fluid Statics.

📋 Worksheet - Fluid Statics.

1. Complete the following statements:

a) The Archimede's force is directly proportional to ...................... of the liquid and ........................ of the body.

b) The hydrostatic pressure is directly proportional to ..................... of the liquid and to ..................... of the liquid.

c) The external pressure exerted on a fluid is transmitted throughout ............. of the liquid and in all ..................... .

d) On a body immersed in a fluid acts the archimedean force having the .................. direction and orientation ........ ..........

Solution:

a) The Archimede's force is directly proportional to the density of the liquid and the volume of the body.

b) The hydrostatic pressure is directly proportional to the density of the liquid and to the depth of the liquid.

c) External pressure exerted on a fluid is transmitted throughout the whole mass of the liquid and in all directions.

d) On a body immersed in a fluid acts the Archimede's force having the vertical direction and the orientation upwards.

2. Write the law that underlies the following applications:

a) Stamping metals.

b) The shuttles.

c) Hydraulic elevator.

d) Ships.

Solution:

a) Stamping metals - Pascal's Law

b) The shuttles - Communicating vessels Law

c) Hydraulic elevator - Pascal's Law

d) Ships - Law of Archimedes

3. Why does a screw in water sink and float in mercury?

Solution:

The archimedean force acts vertically on the screw immersed in a liquid, which is directly proportional to the density of the liquid. As the density of mercury (13600 kg/m³) is much higher than the density of water (1000 kg/m³), the Archimedean force acting on the screw in mercury is also much higher than in water.

4. Determine which of the following statements are true or false:

a) A body with a lower density than the liquid in which it is immersed it floats.

b) Atmospheric pressure does not depend on altitude.

c) The pressure depends on the area of the surface on which the pressing force is distributed.

d) The pressure of the water in a vessel on the bottom of the vessel depends on the area of the support base.

Solution:

a) A body with a lower density than the liquid in which it is immersed it floats. - T

b) Atmospheric pressure does not depend on altitude. – F

c) The pressure depends on the area of the surface on which the pressing force is distributed. - T

d) The pressure of the water in a vessel on the bottom of the vessel depends on the area of the support base. – F

5. A wardrobe weighing 8 kg has a support base of 2000 cm². What pressure does the cabinet exerted on the floor?

Solution:

We write down the problem data and turn it into SI:

We calculate the weight of the body, which is the actual pressing force:
G = m ∙ g = 8 kg ∙ 10 N/kg = 80 N

We apply the pressure formula and replace the problem data:

6. A body of 0,00005 m³ and a weight of 6 N is introduced into the water with a density of 1000 kg/m³. What is the apparent weight of the body when immersed in water?

Solution:

We write down the problem data and turn it into SI:
V_body = 0,00005 m³
G = 6 N
ρ_water = 1000 kg/m³
G_ap = ?

We apply the formula of the Archimedean force in the Law of Archimedes:
F_A = ρ_water ∙ V_body ∙ g = 1000 kg/m³ ∙ 0,00005 m³ ∙ 10 N/kg = 0,5 N

We calculate the apparent weight of the body when immersed in water:
| F_A | = | G - G_ap |
G_ap = G – F_A = 6 N – 0,5 N = 5,5 N