natural
sciences 4
Forces
We can’t see forces but we can feel their effect.
Forces make things:
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
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!
Newton discovered gravity.
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?
GRAVITY
UPTHRUST
HOW do you think GRAVITY and UPTHRUST need to be?
Upthrust needs to be as strong as gravity!