Forces and the Laws of Motion

Warm Up What are the units for: Velocity? Acceleration? Force? A car is driving on the road. How many different forces are acting on the car? What are those forces? Use a diagram to help explain.

Force Force: a push or pull in a certain direction -forces can be balanced or unbalanced -unbalanced forces cause acceleration (change in motion)

Balanced or Unbalanced? Do the examples below represent balanced or unbalanced forces?

Unbalanced forces change motion  e.g. a plane lifting off

Unbalanced forces change motion e.g. tailwind, headwind crosswind

Force continued Forces are measured in Newtons (N) Represented by vectors -Forces have magnitude and direction

Types of Forces FA = Applied Force, applied by an object or a person Fg = Weight, the force at which a massive object attracts another towards itself, directed downward Fn = Normal Force, a force exerted on an object on any surface ; always 90 degrees to the horizontal Ff = Friction, exerted by the surface as an object moves across it and opposes the motion Fair = air resistance or drag is a type of frictional force that acts on objects moving through a fluid and opposes the motion Fbouyancy = buoyant force is a force that opposes the force of gravity in a fluid Flift = BUthe force that opposes we

Free Body Diagrams To analyze the forces on an object, we use Free Body Diagrams

Free Body Diagram Free Body Diagram: a diagram showing the forces acting on an object

Free Body Diagram Example Step 1) Identify forces acting on object Step 2) Draw a diagram of isolated object Step 3) Draw/label vectors for all forces Example: A box is sitting on a table. Draw a FBD

Free Body Diagram Example Step 1) Identify forces acting on object Step 2) Draw a diagram of isolated object Step 3) Draw/label vectors for all forces Example: A box is being pushed on a table. Draw a FBD

Free Body Diagram Example Step 1) Identify forces acting on object Step 2) Draw a diagram of isolated object Step 3) Draw/label vectors for all forces Example: A box is being pulled on a table. Draw a FBD

Free Body Diagram Example Step 1) Identify forces acting on object Step 2) Draw a diagram of isolated object Step 3) Draw/label vectors for all forces Example: A ball is falling to the ground. Draw a FBD.

Free Body Diagram Practice Draw a free body diagram of a 2000 N car driving on the road. The engine gives the car 500 N of force, and friction causes 65 N of force.