Pressure on objects

 After learning this topic, students are expected to be able to:

1. Explain the concept of pressure.
2. Identify the factors that affect pressure.
3. Calculate pressure using the correct formula.
4. Explain pressure in solids, liquids, and gases.
5. Apply the concept of pressure to everyday life.
6. Analyze simple problems related to pressure.

 

1. What Is Pressure?

Pressure is the amount of force acting on a certain area.

In simple words:

Pressure tells us how concentrated a force is on a surface.

Pressure depends on two factors:

• Force (F)
• Area of the surface (A)

The greater the force, the greater the pressure.

The smaller the contact area, the greater the pressure.

 

P = Pressure (Pascal / Pa)
F = Force (Newton / N)
A = Area (square meter / m²)

 

SI Unit of Pressure

The SI unit of pressure is Pascal (Pa).

 

2. Pressure on Solid Objects 

 

A. High-Heeled Shoes

High heels have a small contact area.

Therefore:

Small area → greater pressure

This is why high heels can exert a large pressure on the floor.

B. Sharp Knife

A sharp knife has a very small contact area at its edge.

Therefore, the pressure is large, making it easier to cut objects.

C. Nails

A nail has a sharp tip with a very small area.

The same force produces greater pressure at the tip, allowing the nail to enter wood.

D. Snow Shoes

Snow shoes have a large surface area.

Therefore:

Large area → smaller pressure

This helps prevent a person's feet from sinking deeply into snow.

 

4. Example Calculation

A box is pushed with a force of 200 N. The area of contact between the box and the floor is 0.5 m². Calculate the pressure!

 

 

 5. Pressure in Liquids

Liquids also exert pressure.

Liquid pressure is the pressure produced by a liquid due to its weight.

Liquid pressure depends on:

1. Density of the liquid
2. Acceleration due to gravity
3. Depth of the liquid

The deeper the liquid, the greater the pressure.

 

P = Liquid pressure (Pa)

ρ = Density of liquid (kg/m³)

g = Gravitational acceleration (m/s²)

h = Depth (m)

 

usually 

 

 6. Liquid Pressure in Everyday Life

A. Water Tank
The pressure at the bottom of a water tank is greater than the pressure near the surface.
B. Dam
Dam walls are generally made thicker at the bottom because water pressure increases with depth.
C. Divers
A diver experiences greater water pressure when diving deeper.
D. Bottle with Holes
If a bottle has holes at different heights, water from the lowest hole generally travels farther because the liquid pressure is greater at greater depth.