Do now!

Can you read each others

“Density questions” that

you did for homework?

This lesson – 2.4 Pressure

• Relate (without calculation) pressure to force and area.

• Recall and use the equation P = F/A

Oh no!

YouTube - falling through ice

YouTube - Jason Falls Through Ice

Spread the force over a greater area

Camels

Snow shoes

Tom

Caterpillar tracks

House foundations

My sofa!

Sharp?

I had a dream

Death?

Drawing pins

Pressure

Pressure = Force

AreaN/m2 or Pa

N

m2

Pressure

Pressure = Force

AreaN/m2 or Pa

N

m2

F

AP x

Can you copy this please?

An example

A woman of weight 600N has a total shoe area of 150 cm2 and a man of weight 750 N has a total shoe area of 360 cm2. What is the pressure beneath their feet?

An example

A woman of weight 600N has a total shoe area of 150 cm2 and a man of weight 750 N has a total shoe area of 360 cm2. What is the pressure beneath their feet?

Angelina pressure = force/area = 600/150 = 4 N/cm2

Brad pressure = force/area = 750/360 = 2.1 N/cm2

Bunny Suicides involving pressure

Bunny Suicides involving pressure

Bunny Suicides involving pressure

Bunny Suicides involving pressure

Calculating your own pressureCan you do the

calculations carefully and neatly on the

graph paper to show your pressure (don’t forget you have two feet!) and stick it in

your book

Pressure under a car

Pressure under a car

• Mass = 2000kg

• Weight = mg = 2000x10 = 20000N

• Area = ?

• Pressure = ?

U571

• YouTube - Ocean Odyssey - Ocean Pressure

• YouTube - Styrofoam cup vs. deep sea

• YouTube - U-571 Trailer

Fluid pressure acts in all directions

• Copy!

Pressure and depth

Pressure increases with

depth (P = ρgh)

Let’s try some questions!

Page 63, questions 1 to 4.

That’s it!

• Let’s remind ourselves of what we have done in this unit.

Newton’s 1st Law

If there is no resultant force acting on an object, it will move with constant velocity. (Note the constant velocity could be zero).

Remember?

Newton’s 1st law

If there are no forces, or the forces are balanced – constant velocity

NO RESULTANT FORCE

Pushing force

friction

Newton’s 2nd law

There is a mathematical relationship between the resultant force and acceleration.

Resultant force (N) = mass (kg) x acceleration (m/s2)

F = ma

An example

What will be Mr Porter’s acceleration?

Pushing force (100 N)

Friction (60 N)

Mass of Mr Porter and bike = 100 kg

An example

Resultant force = 100 – 60 = 40 N

FR = ma

40 = 100a

a = 0.4 m/s2

Pushing force (100 N)

Friction (60 N)

Mass of Mr Porter and bike = 100 kg