Introduction to Forces Textbook: 4.3, 4.4 Homework: WS.

Forces A force is a push or a pull Ex. Gravity, Tension, Lift, etc… A vector quantity Given the symbol F Units = 1 kg m/s2 = 1 N Ex. Gravity, Tension, Lift, etc… The four fundamental forces are: gravity, electromagnetic, strong and weak nuclear force

Free Body Diagrams (FBDs) A quick sketch showing all the forces acting on an object Add up all the forces as vectors to determine the total, or net Force (Fnet) Fnet equals the sum of all forces Ex. Draw a FBD of a car speeding up Ex. Draw a FBD of a plane taking off from a runway Ex. Draw a FBD of a skateboarder coasting to a stop Ex. Draw a FBD of an apple hanging from a tree Ex. Draw a FBD of a ball falling with no air resistance Ex. Draw a FBD of a person falling at their terminal velocity

Name of forces Fg = force of gravity Fa = applied force Fk = force of kinetic friction T = force of tension FN = normal force

Drawing FBDs Ex 1. Draw a FBD of an apple hanging from a tree Ex 2. Draw a FBD of a skateboarder coasting to a stop Ex 3. Draw a FBD of a plane taking off from a runway Ex 4. Draw a FBD of a car speeding up

Newton’s First Law (Inertia) An object at rest, remains at rest; an object in motion, remains in motion; unless acted upon by an unbalanced force. Ex. Talk about car accidents Ex. Buses making turns