2. The cause of forces
A force is a push or pull, or any action that has the
ability to change motion.
The key word here is action, force is an action.
Here are some ways of describing forces:
A push
A pull
A stretch
A squeeze
A catch
A twist
3. Forces can make things:
Speed up
Slow down
Change direction
Change shape
4.
5. Units of force
The Newton (N) is a metric
unit of force.
• We use a Newton meter to
measure forces.
It is sometimes called a force
meter.
A force of 1 Newton is the
exact amount of force needed
to cause a mass of 1 kilogram
to speed up by 1 m/s each
second.
6. Example of Newton
One newton (N) is the force it takes to change the speed
of a 1 Kg mass by 1 m/s in 1 second.
One pound of force equals 4.48 newtons.
7. Gravity and weight
The force of gravity on an object is called weight.
Mass and weight are not the same thing.
Mass is an intrinsic property of a body, as it remains the same
everywhere in the universe.
Weight is variable due to change in the magnitude of the
gravitational force applied by the earth.
8. The force vector
A force vector has units of
newtons, just like all forces, but
also includes enough information
to tell the direction of the force.
Positive and negative numbers
indicate opposite directions.
It is sometimes helpful to show the strength and direction
of a force vector as an arrow.
when drawing a force vector, you must choose a scale.
If 1 cm = 1 N, how many newtons of force does this line represent?
9. Forces in springs and ropes
Tension is a force that acts in a rope, string, or other
object that is pulled.
Tension always acts along the direction of the rope.
10. Forces in springs and ropes
When you apply a compression force to a spring, it
collapses to become shorter.
The force created by stretching or compressing a
spring always acts to return the spring to its natural
length.
11. The End
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