Download FORCES

A
push
A
pull
A
twist



Using a spring balance
The unit forces are measured in is the
newton (after Sir Isaac Newton)
The symbol for a newton is
N



We draw forces using an arrow
The arrow shows the direction the force is
acting in
The size of the arrow shows how big or small
the force is
This shows a large force
This shows a small force
A.




eg.
eg.
eg.
eg.
The SPEED of an object
It can make something move
It can speed something up
It can slow something down
It can make something stop moving
hand twisting a door knob
wind pushing on a sail
girl pushing a rock
a stone being pulled towards the earth by the
force of gravity
B The SHAPE of an object
eg. a crashed car
eg. a squashed pillow
C The ENERGY of an object
Eg. the stones gravitational potential energy
changes to kinetic energy when the force of
gravity acts on it
This means that the force acts between objects
that can TOUCH each other
eg. a girl pushing a rock
eg. the force of friction which acts when one
surface is moving across other surface
eg. wind pushing a windmill blade
eg. a girl pulling on a fishing rod
Eg. a bat hitting a ball

This means that the force acts between
objects that DO NOT TOUCH each other
eg. magnetic force
eg. gravitational force
eg. electrostatic force
If the forces on an object are BALANCED
(even on all sides), the object will
KEEP DOING WHAT IT IS ALREADY DOING
This means it will
keep stationary (still)
OR
keep moving at a STEADY (CONSTANT) SPEED
1.
ie. the motion will not CHANGE
2. If the forces on an object are UNBALANCED
(not even on all sides) the object will
CHANGE WHAT IT IS DOING
This means it will
Start moving if it was stationary
OR
If it was already moving the object will
Move faster
Slow down
Turn a corner
ie. the motion will CHANGE
1.
2.
3.
4.
5.
6.
Describe the MOTION (or lack of motion) of the
object to decide whether the forces are balanced
or not
Decide what forces are acting on the object
Draw the force arrows around the object, begin
arrow at the centre of the picture and label them
Make sure the arrow head is facing away from
the picture
Draw large arrows for large forces and small
arrows for small forces
Draw the force of gravity pulling downwards on
all objects on or above the earths surface
Make things change their SHAPE
Eg. crushing a can in a can crusher. The
unbalanced force is downwards
Make things change their DIRECTION
Eg. a bus turning a corner. The unbalanced
force is towards the inside of the turn
When 2 different massesare dropped from
the same height they;
 Travel downwards at the same speed
 Have the same acceleration (they speed up
the same amount)
 Are pulled downwards equally because the
force of gravity on each mass is the SAME
The masses hit the ground
at the same time.
(remember coin/feather and
Galileo’s cannon balls)