Unit 1: Motion, Velocity, Forces

What's position in physics?

where you are relative to a reference point; includes distance and direction, so it's a vector

why is position a vector, not a scalar

because it has both magnitude (distance) and direction

what's the difference between a scalar and a vector?

scalar = magnitude only (mass, temperature, speed)

how can you tell if a quantity is a vector?

if it makes sense to ask "which direction?" it's a vector

what's velocity?

the rate of change of position, including direction; depends on the reference frame

velocity formula

v = ∆x/∆t

difference between speed and velocity

speed = magnitude only

can an object have zero velocity but still be moving?

no, zero velocity means the object is at rest (special case)

what does constant velocity mean?

same speed and direction → zero acceleration

what's a force?

a push or pull; forces are vectors and cause changes in velocity

Newton's First Law (law of inertia)

if the net force is zero, an object stays at rest or moves with constant velocity

what's inertia?

resistance to changes in motion

why does Newton's First Law seem wrong in every day life?

because friction and air resistance act as hidden forces

why does pulling a tablecloth quickly leave objects behind?

inertia dominates when forces act for a very short time.

whats mass?

a measure of inertia; how hard it is to change an object's motion

is mass a vector or a scalar?

scalar