Chapter 11.3 – Motion and Force any action that can change the state of motion of an object, a push or a pull force has magnitude and direction, just like displacement, velocity, and acceleration contact force – push or pull field force – gravity or magnetism

Chapter 11.3 – Motion and Force 4 fundamental forces in nature strong nuclear force – holds protons and neutrons together in the nucleus, strongest force weak nuclear force – responsible for radioactive decay electromagnetic force – responsible for electricity and magnetism, weaker than the strong force gravitational force – responsible for gravity, weaker than EM force

Chapter 11.3 – Motion and Force net force – combination of all forces acting on an object if there is a net force acting on an object, the object accelerates in the direction of the net force if the net force is zero, the forces are balanced and the object does not change its motion

Chapter 11.3 – Motion and Force friction – force that opposes motion between two surfaces that are in contact static friction – friction between stationary surfaces kinetic friction – friction between moving surfaces

Chapter 11.3 – Motion and Force 2 kinds of kinetic friction sliding friction – friction between sliding objects rolling friction – friction from a rounded object rolling over a flat surface friction is necessary for everyday life friction can be lowered with lubricants ex. oil, grease