By Tyieissia and Talal
PERFECT DIVE?
 Some swimming strokes help
reduce the amount of water
resistance when you move
through water. During front
crawl, for example, your body
creates a smooth thin line in the
water and your arms cut through
the water with very little surface
area. Divers try to enter the
water with the least surface area,
too , so they avoid a splash and a
painful belly flop!
HOW WATER RESISTANCE WORKS?
 Water resistance is a type of
friction. When we jump into a
swimming pool, it is water
resistance that prevents us from
hitting the bottom.
 http://www.bbc.co.uk/education
/clips/zxqd7ty
 Some watches are designed
specially to survive the impact of
water resistance when diving into
water.
WHY IS IT HARD WORK TO WALK THROUGH
WATER?
 It is hard to walk through water
because the water is a heavy thing to
walk through. Water has greater
density than air. That is, there are
more molecules in a given volume of
water than in the same volume of air.
So when you walk in water, you have
to displace more matter than walking
through air.
We can show the forces acting on an object using a force diagram.
In a force diagram, each force is shown as a force arrow. An arrow
shows:
The size of the force (the longer the arrow, the bigger the force.)
The direction in which the force acts.
The arrow is usually labelled with the name of the force and its
size in newtons.
Text books often show a force with a thick coloured arrow, but it is
best if you just use a pencil and ruler to draw an arrow with a single
line.
Balanced forces
When two forces acting on an object are equal in size but act in
opposite directions, we say that they are balanced forces.
Nature’s design
 Many sea creatures have streamlined
bodies that help them to move easily
through the ocean water. Sharks and
fish have a slim body, with fins to
help them swim easily through the
water and steer. This means they
use less energy to swim around.
Many boats have been designed in
this same way. Speedboats have a
pointed front that cuts through the
water and air. Sailing boats have a
streamlined shape that glides
through the water, but wide sails
that capture the wind to power them
along.