Hydraulic Machines
WALT- Explain how water pressure may
help us
WILF – Notes taken, questions
answered
1. What do we mean when we say that
a machine is “hydraulic”?
• _____________________________________
___________________________
2. Fill in the gaps by crossing out the
incorrect phrases:
• There are the four key properties of liquids
that are important to remember when looking
at hydraulic machines:
1) Liquids will always (flow to take the shape of
their container/ keep the same shape) no
matter what container you use.
2) If you have a fixed amount of liquid, then its
volume (can change / will always stays the
same) when pressure is applied to it.
3) The pressure in a fluid (acts in all directions /
acts in the direction of the applied force).
4) If a constant force acts throughout a liquid,
the pressure (can vary / stays the same)
throughout the liquid.
Each of these properties can be explained by thinking of the way
particles that
make up the fluid move and interact with each other. How?
3. A mechanic wants to inspect the bottom of a
car for a leak. She tries to lift the car using a
hydraulic lift.
a) On the diagram overleaf, draw and label
arrows to show the direction in which each of
the following forces act:
• The mass of the car acting on its piston
• The force exerted by the mechanic on her
piston
• The hydraulic force of the liquid acting on the
car’s piston
• b) The area underneath the mechanic’s piston
is 0.1m2, and the area underneath the car’s
piston is 10m2. If the car weighs 1000kg, how
much force does the mechanic need to apply
to lift it? (Hint: remember force is measured in
Newtons, not kilograms!)
• **Bonus question**
• c) If the mechanic pushes her piston down by
2 metres, by what distance is the car lifted?
Revision Questions
Oh no!
• YouTube - Man Falls Through Roof 4 times!
• YouTube - Dumb Woman Falls Through Ice
Spread the force over a greater area
Camels
Snow shoes
Caterpillar tracks
House foundations
I had a dream
Sharp?
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 has a weight of 500N and one of her shoes has an
area of 150 cm2. A man of weight 700 N has a shoe area of
360 cm2 (one shoe). What is the pressure beneath their feet?
An example
Mrs Rayner has a weight of 500N and one of her shoes has an area
of 150 cm2. Mr Rayner has a weight of 700 N has a shoe area of
360 cm2 (one shoe). What is the pressure beneath their feet?
Mrs Rayner’s pressure = Force/area = 500/(2 x 150) = 1.67 N/cm2
Man’s pressure = Force/area = 700/(2 x 360) = 0.97 N/cm2
Calculating your own pressure
Remember your
weight in Newtons is
equal to your mass
in kilograms
multiplied by 10.
Calculating your own pressure
Remember your
weight in Newtons is
equal to your mass
in kilograms
multiplied by 10.
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
Really nice car
Pressure under a car
• Mass = 2000kg
• Weight = mg = 2000x10 = 20000N
• Area = 2 x 100mm x 150 mm + 100mm 250
mm
• Pressure = ?
Let’s try some questions!