# 3.1 Types of Forces

```FLOATING AND
DENSITY
WHAT WE KNOW
Objects sink when their mass is greater
than the mass of the fluid they displace.
But what happens if the properties of
the fluid change? For example floating
the same object in canola oil?
BUOYANCY AND DENSITY
Different fluids can have different
densities.
Because density can affect the mass, an
object that may float in one fluid may
not float in another
BUOYANCY AND DENSITY
Have you ever swam in an ocean or a
mineral lake?
Did you notice that it was easier to float in
this water
Because the water is more dense than
freshwater it is heavier. This means that there
is more buoyant force
BUOYANCY AND DENSITY
Warm water is less dense than cold
water.
Because of this ships designed to carry
heavy loads in cold water can sink
lower into the water when traveling in
warm water.
TYPES OF FORCES
CONTACT FORCE
A contact force is one where a
push or pull is exerted when two
things are touching one another
NON-CONTACT FORCE
A non-contact force is one
where a push or pull is exerted
when two things are not actually
touching
EXAMPLES
Buoyant force is a contact force because it
is caused by the particles pushing against one
another
Gravitational force is a non-contact force
because it is caused by the attraction
between earth an an object. This force exists
even if the object is not touching the ground
TIME TO THINK
What kind of force is magnetism?
Non-contact
What kind of force is made by you
when pulling on a rope?
Contact
```
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