Transcript Do now! - MrSimonPorter

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
N
Pressure = Force
Area
N/m2 or Pa
m2
Pressure
F
N
P
x
A
Pressure = Force
Area
N/m2 or Pa
Can you
copy this
please?
m2
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 pressure
Can 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
Remember?
If there is no
resultant force
acting on an
object, it will move
with constant
velocity. (Note the
constant velocity
could be zero).
Newton’s 1st law
If there are no forces, or the
forces are balanced – constant
velocity
Pushing force
friction
NO RESULTANT FORCE
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?
Mass of Mr Porter and bike = 100
kg
Pushing force (100 N)
Friction (60 N)
An example
Resultant force = 100 – 60 = 40 N
FR = ma
40 = 100a
Mass of Mr Porter and bike = 100 kg
a = 0.4 m/s2
Pushing force (100 N)
Friction (60 N)