1. 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

2. 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

3. 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

4. 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

5. 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