Lesson 5

• Nask
• Middelbare school
• havo, vwo
• Leerjaar 2

Pressure in liquids

This lesson

• Recap + exercise
  
• Fluid pressure
• Working on exercises

Learning goals

• Name the formulas for pressure and weight and be able to apply them.
  

• Explain what is meant by liquid pressure.

• Explain why there is greater pressure at the bottom of the sea than at the surface.

Recap

P3 — Pressure & density

• Pressure is the result of force being applied to a surface.
  
• Force is measured in newtons (N)
• area is measured in square meters (m²)

•  The formula for pressure is: 

• The unit of pressure is pascal (Pa). One pascal is 1 N/m²

Pressure=​area​​force​​

P3 — Pressure & density

Weight:

• With how much force an object is pulled down

Weight=mass⋅gravitationalfieldstrength

W=m⋅g

Pressure

ρ=​A​​F​​

pressure=​Area​​Force​​

Pressure (ρ): Pascal (Pa – N/m²), N/cm²

Force (V): N

Area (m): m², cm²

Pressure

w=m⋅g

Weight=mass⋅gravitationalfieldstrength

Weight (W): Newton (N)

Mass (m): kilogram (kg)

Gravitational field strength (g): N/kg

Exercise

Two scenario's:

• 1) A man is standing on 7,60 cm thick ice. He has a mass of 88 kg and one of his feet has an area of 0.0047 m²
  

• 2) A man is laying flat on his back on 7,60 cm thick ice. He has a mass of 88 kg. His body touching the ice has an area of 0.0915 m²
  

Ice of this thickness breaks at about 18.000 Pascal (N/m2). 

The gravitational field strength on Earth is 9.8 N/kg

a) Calculate the pressure for each scenario.

b) Explain wether the ice will break or not.

Liquid pressure

Upthrust

What is upthrust?

Upthrust

Liquid pressure 

And upthrust

To-do for the coming week

Read: 

• 8.3
  
• 8.4

Do:

• 8.3 yellow block + workbook exercises
  
• 8.3 yellow block + workbook exercises
  

Due for the seconds lesson of next week

Learning goals

• Name the formulas for pressure and weight and be able to apply them.
  

• Explain what is meant by liquid pressure.

• Explain why there is greater pressure at the bottom of the sea than at the surface.