Net Force

1
Net Force

• Normal Force
• Frictional Force
• Free Body Diagrams

2
Forces Review

• Yesterday you learned Newtons three laws
• An object with zero or constant velocity will
  remain at zero or with a constant velocity unless
  acted upon by an outside NET force.
• An object experiencing an unbalanced net force
  experiences an acceleration in the direction of
  the net force. (F ma)
• For every force there is an equal and opposing
  force.
• These laws are the basis for the study of dynamics

3
Zero Velocity

• For example a book sitting on a table, is not
  moving and does not move unless acted upon by an
  unbalanced force.
• When it isnt moving there are two forces
  gravity and the table.
• The tables force on the book is known as a
  NORMAL FORCE
• Since the two forces are balanced then the book
  isnt moving. The NET FORCE is zero
• If you remove one of the forces and the net force
  becomes unbalanced then the book accelerates.

4
Constant Velocity

• Constant velocity can be a little more difficult.
• When a car is travelling down the highway at a
  constant speed the forces balance and you have a
  zero net force.
• If you want to accelerate then you need to
  increase the force applied by the engine of the
  car which creates an unbalanced NET FORCE.

5
Frictional Force

• Frictional force depends entirely on the normal
  force applied to an object.
• Depending on how the two types of materials
  interact decides what the force of friction is.
• Force of friction can be calculated using the
  formula