Forces and motion + introduction to mechanics

newton’s first law

applies when resultant force = 0, so a = 0 so velocity is constant or 0

newton’s second law

resultant force = m x a

define a moment of a force about a point

force multiplied by perpendicular distance from line of action of the force to the point

centre of gravity

the point where the entire weight of the object appears to act

centre of mass

the point where the entire mass of an object seems to be concentrated

a couple

a pair of forces acting on a body that are of equal magnitude and opposite direction, acting parallel to one another, but not along the same line

torque of a couple

the rotation force or moment produced

torque of a couple =

force x perpendicular distance between lines of action of the forces

area under a force time graph represents

impulse or change in momentum