10 terms

Mass

A measure of the amount of matter in an object

Weight

A measure of the force of gravity on an object

kg (kilogram)

SI unit for mass

N (Newtons)

SI unit for force (and, therefore, weight, since weight is a force)

Formula to calculate weight from mass

F = mg

Normal Force (Fn)

The perpendicular force exerted by a surface on an object in contact with it; this force prevents objects from pushing through the surface; on a flat surface, it counteracts gravity/weight.

Formula for normal force on a flat surface

Fn = -Fg = -mg

Why is there a negative sign in the normal force equation for an object on a flat surface?

On a flat surface, the normal force counteracts gravity (weight). It is equal in magnitude but is upward, not downward, so we need to multiply weight (which is negative) by -1 to make it positive.

What does g stand for?

g stands for the acceleration due to gravity (-9.81 m/s^2)

Does g stand for gravity?

Nope! g stands for the acceleration due to gravity.