unit 3, dynamics - physics 11

Dynamics

the study of how forces affect the motion of an object

free body diagram

shows one object and all of the forces that are acting on it (ie external forces)

net force

the total or sum of all forces acting on one object

terminal velocity 

point at which a falling object’s drag force is equal to force of gravity FNET=0 

friction

a contact force that opposes slipping along a surface (acting parallel to the surface)

kinetic friction

the force acting in the opposite direction to slipping (it can slow an object down)

static friction

the force preventing slipping (it can cause an object to speed up or slow down)

newton’s first law

an object’s velocity will not change unless it is acted upon by an unbalanced force - if all of the forces acting on one object add up to zero, then the object will not accelerate

newton’s second law

an object’s acceleration is directly proportional to the unbalanced force acting on it and inversely proportional to its mass

newton’s third law

for every action force there is an equal and opposite reaction force - for every force that we draw on one FBD (acting on one object) there is an equal force in the opposite direction on a different FBD (acting on a different object)

Gravity

an attractive force between two masses