NEWTON’S FIRST LAW - INERTIA Chapter 4

Forces and Motion

Newton’s First Law of Motion

What is Mass?

Net Force and Equilibrium ■We may have more than one force acting on an object. ■The net force is the sum of all the forces acting on an object –But remember that forces are vectors, so we have to add up the forces vectorially. ■When all the forces acting on an object add to zero (i.e., the net force is zero) then the object is said to be in equilibrium. ■Forces and Motion BasicsForces and Motion Basics ■Adding ForcesAdding Forces ■Force TutorialForce Tutorial ■Free Body DiagramsFree Body Diagrams

Common Types of Forces ForceDefinitionDirection FrictionA contact force that acts to oppose sliding motion between surfaces Opposite to the direction of sliding NormalA contact force exerted by a surface on an object Perpendicular to and away from the surface SpringA restoring force; the push or pull a spring exerts on an object Opposite to the displacement of the object attached to the spring TensionThe pull exerted by a string or rope when attached to a body and pulled taut Away from the object and parallel to the string or rope at the point of attachment WeightA field force due to the gravitational attraction between two objects, generally Earth and the object Straight down towards the center of the Earth ElectricalA field force due to the electrical charges on two or more objects Attractive (unlike charges) or repulsive (like charges) along the line between the objects

NEWTON’S SECOND LAW Chapter 5 – Force and Acceleration

Mass and Acceleration

Free Fall and Air Resistance ■We’ve seen that objects in free fall all fall with an acceleration equal to g. But that’s true only if we can ignore air resistance. ■When the air resistance on a falling object equals its weight, the net force is zero and no further acceleration occurs. At that point the object has reached its terminal velocity. ■Felix Baumgartner skydiveFelix Baumgartner skydive –Altitude 39 km (24 mi) –Reached an estimated terminal velocity of 1, km/h (843.6 mph), breaking the sound barrier

Force Exercises ■Force InteractiveForce Interactive