Lesson 2 — Recap force, start pressure

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

Pressure

What is force?

Force

A push or pull that changes the way an objects moves.

What is the unit of force?

1. Joule (J)
2. Watt (W)
3. Newton (N)
4. Kilogram (kg)

What are the three effects that a force can have on objects?

Forces can:

• Accelerate or decelerate objects.
  
• Change the direction of a motion.
  
• Change the shape of an object.
  

What is weight?

Weight

The magnitude of the force of earths gravity acting on a specific object.

• A cat has a mass of 4 kg.
  
• The earth pulls on him with a force of 39.2 Newton.
  
• The cat has a weight of 39.2 Newton. 
  

What is the formula for weight?

1. Weight = Force x gravitational field strength
2. W = mass x gravitational field strength
3. Weight = mass x gravitational field strength x height
4. Weight = mass x forces

Demonstration pressure

This lesson

• Recap forces
• Pressure demonstration
  
• The formula for pressure + exercises
  
• To do for the coming week — Working independently
  

Learning goals

• Describe what a forces is and it's three effects on motion.
• Name the unit of force.
• Name the formula for weight.
•  Name the formula for pressure and all the accompanying units.
• Apply the formula for pressure in calculations.

Pressure

ρ=​A​​F​​

pressure=​Area​​Force​​

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

Force (V): N

Area (m): m², cm²

Exercise

a) Find the pressure exerted by a force of 72 Newtons on an area of 6 m2. Give your answer in N/m2.

Exercise

a) Find the pressure exerted by a force of 72 Newtons on an area of 6 m2. Give your answer in N/m2.

Lets look at the yellow block exercises

Exercise

A woman weighing 76 kg is wearing high heels to the zoo. She goes to see an elephant with a mass of 5221 kg. One of her heels has a total area of 8.4 cm2. One of the elephants feet has an area of 301 cm2.

a) Without making calculations, make an estimation of wether the elephant or the women applies a greater pressure to the ground. Write down your reasoning.

b) Calculate the pressure the women applies to the ground.

c) Calculate the pressure the elephant applies to the ground.

Next week — to do list

Read:

• 8.1
  
• 8.2
  

Do:

• 8.1 yellow block exercises
  
• 8.1 workbook exercises
  
• 8.2 yellow block exercises
  
• 8.2 workbook exercises
  

Learning goals

• Describe what a forces is and it's three effects on motion.
• Name the unit of force.
• Name the formula for weight.
•  Name the formula for pressure and all the accompanying units.
• Apply the formula for pressure in calculations.