Good Science Victorian Curriculum Year 7

PHYSICAL SCIENCES
8.3
THE SIZE AND
DIRECTION OF
FORCES
LEARNING INTENTION
At the end of this lesson I will be
able to identify characteristics
of specific forces in terms of size
and direction.
KEY TERMS
1
Every moment of the day, you’re either applying forces to
objects or having forces applied to you.
Each force has two key characteristics. The direction of the
force affects the direction that an object moves, and whether
it slows down or speeds up. The size, or magnitude, of the
force affects how much the object might move, or how quickly
it speeds up or slows down.
Every force acts in a certain direction
A force is shown in a diagram as an arrow that points outwards from an
object. The direction that the arrow is pointing indicates which way the
force is acting on an object.
Imagine you and your family are at the supermarket, and you’re
handling a shopping trolley. In what directions could you apply force?
magnitude
the size or power of an object,
energy or force
net force
the sum of all forces acting
on an object
1
You could push the trolley.
This applies force in a forwards
direction and makes the trolley
move that way.
Force
Motion
LITERACY LINK
WRITING
2
You could pull the trolley to
make it move backwards.
Force
Outline a situation in which you
have had to think about both the
size and direction of a force that
you’ve applied to an object.
NUMERACY LINK
UNITS
3
You could try swinging the
handle to the side to make
it spin. The force is directed
to the side of the trolley, but
the motion is a turn, rather
than a sideways push.
Force
Motion
Motion
The formula to convert kilograms
to newtons is:
1 kg = 9.807 N
Convert these to newtons:
a 1 kg
b 5 kg
c 120 kg
4
If you started running while
pushing the trolley ahead of
you, you could keep pushing
on it to make it go faster.
Force
Increasing
speed
5
The only way to stop the trolley
quickly would be to apply a
force in the opposite direction.
Force
Motion
Decreasing
speed
124 GOOD SCIENCE VICTORIAN CURRICULUM 7