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natural
Forces
We can’t see forces but we can feel their effect.
Forces make things:
• move or stop
• change shape
• break
• fall to the ground
• stay still
• float or sink
Forces can be…
PUSH OR PULL
CONTACT AND NON-CONTACT
BALANCED OR UNBALANCED
Do you know how magnets work?
Magnets create a magnetic field around them.
This force attracts objects made of iron and steel.
This is a photo of a magnet and iron filings. The iron filings
show us where the magnetic field is.
Magnets attract and repel!
Opposite poles attract.
Same poles repel.
Gravity
Newton discovered gravity.
Gravity is a non-contact, pull
force.
All masses have gravity. It is a
force that pulls towards their
centre.
This force is only noticeable with
very large masses, for example,
planets.
The Earth’s gravity pulls
everything on or near the Earth
towards its centre. This stops us
and our belongings floating away!
What’s weight?
Weight is the force with which
we are attracted to the ground.
It depends on:
GRAVITY (N) and
our MASS (kg, amount of matter).
[weight = mass x gravity]
What’s upthrust?
Upthrust is a contact, push force applied by water and air.
It pushes objects in air and water up.
The bigger the VOLUME, the bigger the upthrust.
Why do we float?
HOW do you think GRAVITY and UPTHRUST need to be?
Upthrust needs to
be as strong as
gravity!
GRAVITY
UPTHRUST