Forces & Free Body Diagrams Aim: How can we account for multiple forces acting on a single object?

Types of Forces Net Force ( F Net ) – The SUM of all the forces acting on an object Applied Force ( F App ) – Any type of force that actively PUSHES or PULLS an object Weight/Gravitational Force ( F g ) – The PULLING force of gravity, giving objects weight – ALWAYS STRAIGHT DOWN Normal Force ( F N ) – A force that PUSHES on an object from a surface; always PERPENDICULAR to the surface Friction ( F f ) – A RETARDING force that OPPOSES motion Tension ( F T ) – A PULLING force provided by a STRING/CABLE/CHAIN etc.

FREE BODY DIAGRAMS (FBD) Vector diagram of ALL forces that are acting on an object All vectors “should” point outwards from the center of the object All vectors should face the CORRECT DIRECTION with a proper length that AGREES with its value

A 50kg wood crate is stationary on a flat, level, frictionless floor. Draw the FBD and calculate the weight and normal force FNFN FgFg When an object is STATIONARY or MOVING AT CONSTANT VELOCITY, the SUM OF ALL FORCES MUST EQUAL ZERO

A force of 300N is applied straight down on the top of the 50kg wood crate. The crate is still stationary on a flat, level, frictionless floor. Draw the FBD and calculate the weight and normal force FNFN FgFg F App = -300N

A rope applies an upward force of 300N straight upward from the top of the 50kg wood crate. The crate is still stationary on a flat, level, frictionless floor. Draw the FBD and calculate the weight and normal force FNFN FgFg F T = 300N

The 50kg crate is now transported to a rough, flat, level floor. A worker pushes the crate at a constant speed to the right with a force of 200N. Draw the FBD and calculate all the forces acting on the crate FNFN FgFg F App = 200N FfFf

The combined mass of Anna, Kristof, Olaf and the sleigh is 630kg, (a) calculate the weight of the sleigh and the normal force acting on it. (b) If there is 300N of friction and Sven pulls with a force of 440N how quickly does the sleigh accelerate? F f = 300N F App = 440N

A man pushes a 1000kg car that ran out of gas. If the car accelerates at 0.11m/s 2 when he applies a 6800N force, how much friction must he overcome? F App FfFf

Forces at an Angle When a force is applied at an angle, the COMPONENTS of that force must be calculated first Once the components are calculated, the original angled force can be ignored Then solve the rest of the problem as you normally would

In curling (the most epic sport of all sports), a woman applies a downward force of 290N at an angle of 60° below the –x-axis. If there is negligible friction between the 1.2kg “broom” and the ice, calculate how quickly the broom will accelerate to the left F App = 60° below –x-axis FNFN FgFg

During crossfit training, Chad pulls a 75kg sled with a force of 500N at an angle of 25°. Assume there is 350N of friction, (a) determine the horizontal acceleration of the sled and (b) determine the normal force. FNFN FgFg F App = 25° F f = 350N

During crossfit training, Chad pulls a 75kg sled with a force of 500N at an angle of 25°. Assume there is 350N of friction, (a) determine the horizontal acceleration of the sled and (b) determine the normal force. FNFN FgFg F App = 25° F f = 350N